Long Strange Trip - on Amazon Prime and I highly recommend it.
First thing to discuss is the length. Some may be scared off the documentary because they've heard it is 4 hours long, which is true. However, Amazon Prime has broken it into 6 cohesive "acts" or episodes which is very manageable. This is easily one of the top 5 music related documentaries I've ever seen (I'll have to do that list soon).
The documentary follows the band from its formation and its crucible of the "acid test" to the death of Jerry Garcia. From a band going out on the road and coming back as broke as when they departed to the money making machine they became at the end. Some very amusing and insightful stories were told along the way.
Now I know some would argue that there has not been an end and that the Dead lives on but Dead and Company or the other band offshoots are just not the same (although I must admit I'm thinking about seeing them at Fenway Park this summer).
So watch the documentary. I think you'll enjoy it.