Fair Value Measurement - Level 3 Analysis (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Level 3 Analysis - Supplemental Data [Abstract]
Percentage of level 3 assets in total Firm assets	0.60%		0.60%
Total realized/unrealized gains/(losses)	$ (602)	$ 510	$ 78	$ 1,550
Recurring
Level 3 Analysis - Supplemental Data [Abstract]
Assets fair value	837,597		837,597		$ 680,612
Recurring | Level 3
Level 3 Analysis - Supplemental Data [Abstract]
Assets fair value	16,543		16,543		$ 17,165
Decrease in level 3 assets	553		622
Recurring | Level 3 | Liabilities
Level 3 Analysis - Supplemental Data [Abstract]
Total realized/unrealized gains/(losses)	(615)	504	(2,100)	822
Recurring | Level 3 | Assets
Level 3 Analysis - Supplemental Data [Abstract]
Total realized/unrealized gains/(losses)	(1,500)	$ 278	(1,000)	$ 1,700
Recurring | Level 3 | MSRs
Level 3 Analysis - Supplemental Data [Abstract]
Decrease in level 3 assets	$ 1,000		$ 1,000