Long-Term Debt and Shareholders' Equity (Amounts Reclassified from AOCI) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans	$ 492	$ 514	$ 980	$ 1,046
Income tax expense	101	16	190	18
Net income	354	66	676	80
Net unrealized gains (losses) on derivatives and other | Amounts reclassified from AOCI
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and fees on loans	15	13	31	17
Income tax expense	4	3	8	4
Net income	$ 11	$ 10	$ 23	$ 13