Parent Company (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Non-interest revenues
Gain on sale of securities									$ 0	$ 0	$ 0
Other									1,732	2,029	2,033
Total non-interest revenues									27,030	26,348	26,896
Interest income									8,553	7,475	7,545
Interest expense									2,112	1,704	1,623
Total revenues net of interest expense	$ 8,839	$ 8,436	$ 8,307	$ 7,889	$ 8,022	$ 7,774	$ 8,235	$ 8,088	33,471	32,119	32,818
Expenses
Salaries and employee benefits									5,258	5,259	4,976
Other									5,776	5,162	6,793
Total Expenses									23,298	21,997	22,892
Pretax loss	1,821	1,827	1,949	1,817	1,161	1,735	3,016	2,184	7,414	8,096	7,938
Income tax provision (benefit)									4,678	2,688	2,775
Net income	$ (1,197)	$ 1,356	$ 1,340	$ 1,237	$ 825	$ 1,142	$ 2,015	$ 1,426	2,736	5,408	5,163
Parent Company [Member]
Non-interest revenues
Gain on sale of securities									0	0	0
Other									358	391	400
Total non-interest revenues									358	391	400
Interest income									258	196	172
Interest expense									493	515	526
Total revenues net of interest expense									123	72	46
Expenses
Salaries and employee benefits									362	388	341
Other									553	510	443
Total Expenses									915	898	784
Pretax loss									(792)	(826)	(738)
Income tax provision (benefit)									(354)	(327)	(268)
Net loss before equity in net income of subsidiaries and affiliates									(438)	(499)	(470)
Equity in net income of subsidiaries and affiliates									3,174	5,907	5,633
Net income									$ 2,736	$ 5,408	$ 5,163