Fair Value (Schedule of Assets and Liabilities Measured at Fair Value by Class on a Recurring Basis Using Level 3 Inputs) (Details) - Level 3 - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Private equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of assets, Beginning balance	$ 72	$ 77	$ 80	$ 107
Unrealized securities gains (losses), net	10	1	79	(24)
Other noninterest income (expense)	0	0	0	0
Purchases	4	3	10	7
Cost of investments sold	(13)	0	(19)	(9)
Transfers out	(1)	0	(78)	0
Fair value of assets, Ending balance	72	81	72	81
Ag loan svcg and int-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Fair value of assets, Beginning balance	15	17	16	18
Unrealized securities gains (losses), net	0	0	0	0
Other noninterest income (expense)	(1)	0	(2)	(1)
Purchases	0	0	0	0
Cost of investments sold	0	0	0	0
Transfers out	0	0	0	0
Fair value of assets, Ending balance	$ 14	$ 17	$ 14	$ 17