Fair Value Measurement - Level 3 Analysis (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Level 3 Analysis - Supplemental Data [Abstract]
Percentage of level 3 assets in total Firm assets	0.60%
Total realized/unrealized gains/(losses)	$ 680	$ 1,040
Recurring
Level 3 Analysis - Supplemental Data [Abstract]
Assets fair value	808,746		$ 680,612
Recurring | Level 3
Level 3 Analysis - Supplemental Data [Abstract]
Assets fair value	17,096		$ 17,165
Decrease in level 3 assets	69
Recurring | Level 3 | Liabilities
Level 3 Analysis - Supplemental Data [Abstract]
Total realized/unrealized gains/(losses)	(1,500)	318
Recurring | Level 3 | Assets
Level 3 Analysis - Supplemental Data [Abstract]
Total realized/unrealized gains/(losses)	$ 505	$ 1,500