Variable Interest Entities (Details) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Variable Interest Entity [Line Items]
Variable interest entity, other short-term borrowings	$ 610		$ 620
Weighted average life of trusts	2 years 2 months 12 days	2 years 8 months 12 days
Assets	$ 326,528		314,706
Liabilities	301,361		288,506
VIE - primary beneficiary
Variable Interest Entity [Line Items]
Assets	0		17
Liabilities	0		4
Potential maximum loss exposure of unconsolidated funds			13
VIE - not primary beneficiary
Variable Interest Entity [Line Items]
Potential maximum loss exposure of unconsolidated funds	17		22
State and political subdivisions, securities in trusts
Variable Interest Entity [Line Items]
Investment securities related to state and political subdivisions	$ 690		$ 700

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