Parent Company Financial Statements - Parent Company Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Assets
Cash and due from banks	$ 2,243	$ 1,897
Interest-bearing deposits with banks	343	1,895
AFS securities at fair value	24,547	26,926
HTM securities at amortized cost	23,027	16,680
Other assets	14,235	14,046
Total assets	221,642	219,276	$ 209,947
Liabilities and Shareholders' Equity:
Short-term borrowings	4,938	1,406
Long-term debt	23,648	21,965
Accounts payable and other liabilities	5,990	5,745
Total liabilities	191,947	189,350
Total shareholders' equity	29,695	29,926	$ 27,340	$ 24,377
Total liabilities and shareholders’ equity	221,642	219,276
Parent Company
Assets
Cash and due from banks	13	21
Interest-bearing deposits with banks	6,365	7,094
AFS securities at fair value	133	134
HTM securities at amortized cost	1	1
Advances to / receivables from subsidiaries	6,118	3,831
Investment in subsidiaries	29,219	29,723
Other assets	66	131
Total assets	41,915	40,935
Liabilities and Shareholders' Equity:
Short-term borrowings	7	46
Long-term debt	12,042	10,836
Accounts payable and other liabilities	171	127
Total liabilities	12,220	11,009
Total shareholders' equity	29,695	29,926
Total liabilities and shareholders’ equity	41,915	40,935
Parent Company | Banking
Assets
Advances to / receivables from subsidiaries	2,454	850
Investment in subsidiaries	27,846	28,444
Parent Company | Nonbank
Assets
Advances to / receivables from subsidiaries	3,664	2,981
Investment in subsidiaries	$ 1,373	$ 1,279