Question For Hilton Als

The article we read on Jane Fonda by Hilton Als was a great read filled with wonderful detail.  I would ask Als how he got all of those details from so many different situations over such a long period of time. Was he actually there for all of them?  This article read like new journalism to me and I would be curious as to how he got details like what Fonda was drinking at her kids wedding, what her husband said in his speech, etc.