Parent Company Financial Information - Parent Company Condensed Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and due from banks	$ 4,084	$ 2,753
Interest-bearing deposits with banks	14,981	1,091
Available-for-sale Securities	74,727	25,038
Other Assets	31,832	13,470
Total assets	473,078	225,697
Liabilities and Equity [Abstract]
Short-term borrowings	18,218	5,178
Long-term debt	41,339	23,709
Other Liabilities	12,236	5,433
Total liabilities	406,520	195,519
Total shareholders' equity	66,558	30,178	$ 29,695	$ 29,926
Total liabilities and shareholders' equity	473,078	225,697
Parent Company
Assets
Advances to / receivables from subsidiaries:	5,085	7,097
Investment in subsidiaries:	68,062	29,567
Cash and due from banks	361	130
Interest-bearing deposits with banks	12,031	7,102
Available-for-sale Securities	137	132
Other Assets	655	52
Total assets	86,331	44,080
Liabilities and Equity [Abstract]
Short-term borrowings	603	2
Long-term debt	18,130	13,709
Other Liabilities	1,040	191
Total liabilities	19,773	13,902
Total shareholders' equity	66,558	30,178
Total liabilities and shareholders' equity	86,331	44,080
Parent Company | Banking
Assets
Advances to / receivables from subsidiaries:	1,350	2,608
Investment in subsidiaries:	64,206	28,070
Parent Company | Nonbank
Assets
Advances to / receivables from subsidiaries:	3,735	4,489
Investment in subsidiaries:	$ 3,856	$ 1,497