Variable Interest Entities (Details) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Variable Interest Entity [Line Items]
Investment securities related to state and political subdivisions	$ 870		$ 940
Variable interest entity, other short-term borrowings	$ 770		820
Weighted average life of trusts	2 years 7 months 6 days	3 years
Assets	$ 280,242		245,610
Liabilities	255,369		221,179
VIE - primary beneficiary
Variable Interest Entity [Line Items]
Assets	17		21
Liabilities	4		5
Potential maximum loss exposure of unconsolidated funds	13		16
VIE - not primary beneficiary
Variable Interest Entity [Line Items]
Potential maximum loss exposure of unconsolidated funds	$ 20		$ 21