Just to fill in a couple gaps: The attack lasted approximately 3 hours, starting by draining the largest accounts and moving down from there over time. It's known not all of them were stolen. I've seen estimates (by outsiders) that approx. 60+% of bitcoins were stolen. It was certainly more than 36%.

Edit: Sources:

https://www.reddit.com/r/Bitcoin/comments/4wizdn/txid_and_bi...

https://www.reddit.com/r/Bitcoin/comments/4wmpzt/bitfinex_as...