Parent Company Financial Information - Parent Company Condensed Income and Comprehensive Income Statements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income:
Other Interest and Dividend Income	$ 108	$ 66	$ 52
Expenses:
Interest Expense	2,096	1,438	839
Other expense	7,934	6,932	7,444
Income tax benefit	(782)	(803)	(911)
Net income	3,237	3,257	2,415
OCI	871	(248)	(88)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	4,108	3,009	2,327
Parent Company
Income:
Dividends from subsidiaries	1,685	2,972	1,990
Other Interest and Dividend Income	217	164	112
Other income	0	7	2
Total income	1,902	3,143	2,104
Expenses:
Interest Expense	475	364	227
Other expense	250	82	83
Total expenses	725	446	310
Income before income taxes and equity in undistributed earnings of subsidiaries	1,177	2,697	1,794
Income tax benefit	92	52	63
Income before equity in undistributed earnings of subsidiaries	1,269	2,749	1,857
Equity in undistributed earnings of subsidiaries in excess of dividends from subsidiaries	1,968	508	558
Net income	3,237	3,257	2,415
OCI	871	(248)	(88)
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest	4,108	3,009	2,327
Parent Company | Nonbank
Income:
Dividends from subsidiaries	35	147	40
Parent Company | Banking
Income:
Dividends from subsidiaries	$ 1,650	$ 2,825	$ 1,950