What comes through most in “Woody Allen: A Documentary,” Robert Weide’s thoroughgoing two-part PBS profile of the nebbishy auteur, is that Allen, who has made such a career out of neuroses, phobias and other assorted worries, seems nearly unaffected by what anyone has ever said about him or his work.

That’s a shame, if only because so much has been said and written about Allen. Millions of words, thousands of column inches, entire film-theory dissertations, bestselling biographies; critical raves, pans and verbose analyses. Entire forests have fallen so that people could tell other people what they think of Woody Allen and what his movies have meant. (And still another forest fell in the tabloid chronicling of his scandalous breakup and custody battle with Mia Farrow in the 1990s.) None of it ever made much of a dent, according to the man himself.

“Woody Allen” does a nice job of surmounting all that has been said before and packaging it into a tidy, informative mini-epic. The film, part of the “American Masters” series, is helped immensely by the fact that Allen, who will turn 76 on Dec. 1, cooperated happily and at quite some length, granting Weide lots of access to his closest collaborators and his thought processes. He answers questions this time around about his work and life in ways that he’s been reluctant to do in the past. Even now, he is still far too humble. When he saw the finished print of his 1979 film “Manhattan,” one of his greatest, he recalls being so sickened that he offered United Artists an entirely new movie, free of charge, if they’d agree to shelve it.

At 195 minutes in length (split in two partsis exhaustive without being overwhelming., Sunday and Monday nights at 9 p.m. on most PBS stations), “Woody Allen” It’s not entirely clear why the time has come for what, in some moments, feels like a sunset homage — especially because Allen is still cranking out a film every year, is physically fit and had parents who lived to the ages of 96 and 100. His most recent film, “Midnight in Paris,” has become his biggest box-office hit. “My relationship with death remains the same,” Allen is seen telling a press conference at a film festival. “I am strongly against it.” There is no indication that he intends to slow down.

Nevertheless, the time has come to talk about methods, theories, inspiration, legacy. This includes opening the nightstand drawer in his master bedroom, where Allen keeps a disorganized pile of scraps of paper on which he has jotted stray ideas for movies. When it’s time to make another one (which is always), he returns to this drawer to scrounge around for a little more brilliance.

* * *

“Woody Allen” begins with his unremarkable if slightly odd Brooklyn boyhood (he was born Allen Stewart Konigsberg); his utter failure as a student (“I hated school with a passion. . . . To this day I think of it as a curse,” he says, walking past P.S. 99); his early love for films at the neighborhood Jewel theater (immortalized in 1985’s “The Purple Rose of Cairo”), and how his childhood memories have inspired scenes or themes in some of his movies. The documentary then works forward chronologically with Allen’s earliest attempts at writing and performing stand-up comedy in Manhattan nightclubs and Upstate resort towns.

As his shtick catches on, he becomes a go-to 1960s proto-nerd, making himself available to variety shows and talk shows to kvetch and crack one-liners about romance or life’s little annoyances (eons before Jerry Seinfeld) or partake in stunts such as getting in the boxing ring with a kangaroo on “Hippodrome” in 1966. (Or, on a different TV show appearance, sing “Little Sir Echo” with a howling pooch.)

We’ve become so accustomed to Allen looking like an old man these days that to see him as a striving young buck, full of exuberance (or, at least, the Woody Allen version of exuberance) may be something of a revelation to younger viewers.

Therefore, when Diane Keaton — who has been Allen’s muse, co-star and ex-lover — expounds on how she was irresistibly attracted to the man, it begins to make sense when you see him in action, circa 1970. Belatedly, perhaps, one awakens to the notion of the sex appeal behind the horn-rimmed glasses. That’s not news to those in whom Allen’s pre-“Annie Hall” zaniness inspired geek lust, but it might be news to viewers in 2011.

Funny equals sexy, and vice versa. “Woody Allen,” though intent on cracking the enigmatic emotional armor of its subject, makes great use of old interview footage where Allen was just tossing out riffs and jokes in his early years. In one clip, from the early ’70s, a British interviewer asks him: “Who was the first movie star you met, can you remember?”

“Uh, yes,” Allen deadpans. “I met Trigger, who was Roy Rogers’s horse, um, at a party.Actually, I picked him up at a party, and we had an ongoing relationship for two years after that. Which I’m very proud of.”

“Did you ever meet Roy Rogers at that time?” the interviewer asks, starting to giggle, while Allen remains completely stone-faced, chin in hand.

“No, I had no interest in meeting Roy Rogers. But I loved living with his horse.”

“But what about the smell?”

“[Trigger] didn’t mind that so much.”

* * *

Then come the movies, nearly four dozen of them and counting, depending on what you’re counting.

Pained by his debut work in the 1965 slapstick comedy “What’s New, Pussycat?”(which he wrote and performed in) and soothed not one bit by its box-office success, Allen embarked on a career in which his own autonomy and control over the final cut had to be guaranteed.

“Woody Allen” thus becomes a serious exploration of staying true to one’s sensibility and ignoring buzz at any cost. It builds its case for Allen’s genius by examining his films in order — a true treat for loyal fans and perhaps even ambivalent critics. The documentary is enriched greatly by candid interviews with all of Allen’s closest associates (producers, his casting director, cinematographers) and his muses, including Keaton; his second wife, Louise Lasser; “Manhattan” co-star Mariel Hemingway.

Part 1 concludes with the critical disappointment of 1980’s “Stardust Memories,” which was such a comedown for Allen’s devotees after the success of “Annie Hall” and “Manhattan.” Part 2 is about Allen’s continued evolution through the ’80s and ’90s toward the tragic, the comic and, most perfectly, the tragicomic.

It goes without saying that Mia Farrow doesn’t turn up to share her own special knowledge about the enigma that is Allen, given the couple’s explosive breakup after he began a relationship with Farrow’s then-21-year-old daughter, Soon-Yi Previn. (Allen and Previn married and have been together for 19 years now.) Allen speaks of Farrow so politely here, with respect for her talent and dedication to their many movies together. Everyone interviewed is kind and so careful to use past-tense verbs when speaking of her that it might come as a shock to some viewers to learn that Farrow is still alive.

But she is nonexistent in the particular, by-the-book routine world Allen has built for and around himself, including a rosy vision of New York that Allen himself is the first to admit is a fantasy, and only Martin Scorsese is willing to criticize as being too unreal. It’s a Manhattan nearly devoid of the poor or minorities. The only poor people he liked portraying were scraping by in the Great Depression or war era.

Though it doesn’t need to be longer, “Woody Allen” could stand to exchange some of its admiration for a more analytical look at how Allen frankly and subtly interpreted, mocked and celebrated the Jewish American experience in his material. It should also, at some point, have addressed the near-absence of black people in his films (“Deconstructing Harry” and “Melinda and Melinda” being two unnotable exceptions), even though Chris Rock is interviewed for the documentary and probably would have been glad you asked.

This is worth bringing up, because Allen will go down in history as one of America’s finest filmmakers, whose appeal was nevertheless limited, as if meant only for “sophisticated” moviegoing audiences. Is that limited appeal some kind of appealing limitation? Do the subliminal class cues — the nice apartments, the buoyant social gatherings at which the protagonist nevertheless experiences existential ennui — cast a disproportionate charm spell on the discerning filmgoer, especially now that Allen is applying the same idealized rinse to films set in London, Barcelona and Paris?

That’s probably material for someone’s else documentary. Fan of Allen’s oeuvre, meanwhile, will enjoy putting faces and voices to the names we’ve seen set in requisite, plain white Windsor font in the credits of his movies, and they offer invaluable insight into how Allen writes, directs and frets over his projects — and how swiftly he moves on to the next one. They are particularly helpful at recalling how he coped with the tabloid deluge that accompanied the Farrow split, especially in a montage in which, to a person, they talk about Allen’s ability to “compartmentalize” not only his emotions but how he deals with the world around him.

By being so thorough a review of his many works, “Woody Allen” will remind viewers of how many mediocre films we’ve sat through in dumpy art-house theaters, simply because his name was on them. The clunkers are as much a part of his story as “Annie Hall, “Hannah and Her Sisters” and “Crimes and Misdemeanors” (and later, “Bullets Over Broadway,” “Match Point” and “Vicky Cristina Barcelona”).

As his most faithful moviegoers know all too well — and as Allen talks about with a whiff of his studied despair — the brilliance doesn’t always come. But it does keep coming, like clockwork.

How? Why? “Woody Allen” is the closest we’ve ever come to learning the answers.

American Masters: Woody Allen — A Documentary

(195 minutes, in two parts) airs Sunday and Monday at 9 p.m. on WETA and MPT.