Derivative Instruments and Hedging Activities - Notional and Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 142,938	$ 105,916
Derivative Assets, Gross Amount	1,494	1,518
Derivative Liabilities, Gross Amount	1,438	520
Derivative Asset, Netting Adjustment	(539)	(532)
Derivative Liability, Netting Adjustment	(336)	(143)
Derivative Assets	955	986
Derivative Liability	1,102	377
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	98,896	73,009
Derivative Assets, Gross Amount	717	1,043
Derivative Liabilities, Gross Amount	865	209
Derivatives designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	90,880	64,867
Derivative Assets, Gross Amount	446	717
Derivative Liabilities, Gross Amount	856	207
Derivatives designated as accounting hedges | Interest rate contracts | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	40,480	34,417
Derivative Assets, Gross Amount	295	550
Derivative Liabilities, Gross Amount	569	146
Derivatives designated as accounting hedges | Interest rate contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	50,400	30,450
Derivative Assets, Gross Amount	151	167
Derivative Liabilities, Gross Amount	287	61
Derivatives designated as accounting hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	8,016	8,142
Derivative Assets, Gross Amount	271	326
Derivative Liabilities, Gross Amount	9	2
Derivatives designated as accounting hedges | Foreign exchange contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	5,620	5,580
Derivative Assets, Gross Amount	108	239
Derivative Liabilities, Gross Amount	9	2
Derivatives designated as accounting hedges | Foreign exchange contracts | Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	2,396	2,562
Derivative Assets, Gross Amount	163	87
Derivative Liabilities, Gross Amount	0	0
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	44,042	32,907
Derivative Assets, Gross Amount	777	475
Derivative Liabilities, Gross Amount	573	311
Derivatives not designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	42,275	32,025
Derivative Assets, Gross Amount	720	475
Derivative Liabilities, Gross Amount	559	307
Derivatives not designated as accounting hedges | Interest rate contracts | MSRs
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,696	1,665
Derivative Assets, Gross Amount	17	11
Derivative Liabilities, Gross Amount	21	7
Derivatives not designated as accounting hedges | Interest rate contracts | Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	39,474	28,841
Derivative Assets, Gross Amount	670	431
Derivative Liabilities, Gross Amount	530	290
Derivatives not designated as accounting hedges | Interest rate contracts | Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,105	1,519
Derivative Assets, Gross Amount	33	33
Derivative Liabilities, Gross Amount	8	10
Derivatives not designated as accounting hedges | Other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,767	882
Derivative Assets, Gross Amount	57	0
Derivative Liabilities, Gross Amount	$ 14	$ 4