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	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Private equity investments
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of year	$ 107	$ 102
Securities gains (losses), net	(5)	2
Other noninterest income (expense)	0	0
Purchases	9	10
Redemptions and paydowns	0	0
Other	(31)	(7)
Balance at end of year	80	107
Ag loan svcg and int-only strips
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance at beginning of year	18	18
Securities gains (losses), net	0	0
Other noninterest income (expense)	(1)	1
Purchases	0	0
Redemptions and paydowns	(1)	(1)
Other	0	0
Balance at end of year	$ 16	$ 18