Long-Term Debt and Shareholders' Equity (Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans	$ 484	$ 505	$ 1,464	$ 1,551
Income tax expense	71	40	261	58
Net income	240	175	916	255
Net unrealized gains (losses) on derivatives and other | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans	16	16	46	32
Income tax expense	4	4	11	8
Net income	$ 12	$ 12	$ 35	$ 24