Deposits (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total deposits	$ 129,248	$ 118,579	$ 116,118
Time Deposits, $250,000 or More [Abstract]
Time Deposits, $250,000 or More	18,644	20,326
Time Deposits, Fiscal Year Maturity [Abstract]
0-90 days	11,392
91-180 days	4,389
181-365 days	4,199
2017	19,980
2018	871
2019	704
2020	919
2021	1,184
Later years	3,031
Time deposits	26,689
Overdraft deposits	442	327
Domestic Deposits [Member]
Time Deposits, $250,000 or More [Abstract]
Time Deposits, $250,000 or More	14,419	16,288
Time Deposits, Fiscal Year Maturity [Abstract]
0-90 days	9,911
91-180 days	2,941
181-365 days	2,878
2017	15,730
2018	870
2019	703
2020	918
2021	1,184
Later years	3,031
Time deposits	22,436
Foreign Deposits [Member]
Time Deposits, $250,000 or More [Abstract]
Time Deposits, $250,000 or More	4,225	$ 4,038
Time Deposits, Fiscal Year Maturity [Abstract]
0-90 days	1,481
91-180 days	1,448
181-365 days	1,321
2017	4,250
2018	1
2019	1
2020	1
2021	0
Later years	0
Time deposits	$ 4,253