Accounting Policies - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change	$ 6,340	$ 6,321	$ 6,340	$ 6,321	$ 6,126		$ 6,269	$ 6,090	$ 4,972
Assets of managed investment entities	73,110		73,110				70,130
Liabilities of managed investment entities	66,770		66,770				63,861
Operating lease liability	175		175				180
Operating lease right-of-use asset	$ 154		$ 154				158
Weighted average common shares adjustment related to stock-based compensation (shares)	300,000	1,100,000	500,000	1,200,000
Anti-dilutive potential common shares related to stock-based compensation plans (shares)	0	0	0	0
Maturities of short term investments			3 months
New collateralized loan obligation temporary warehousing entity
Significant Accounting Policies [Line Items]
Assets of managed investment entities	$ 140		$ 140
Liabilities of managed investment entities	130		130
Retained Earnings
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change	$ 3,737	$ 4,022	$ 3,737	$ 4,022	$ 3,685		$ 4,009	$ 3,914	$ 3,588
Cumulative effect adjustment in period of adoption | Retained Earnings | Accounting Standards Update 2016-13
Significant Accounting Policies [Line Items]
Cumulative effect of accounting change						$ 7