Derivative Instruments and Hedging Activities - Notional and Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 113,970	$ 105,916
Derivative Assets, Gross Amount	2,023	1,518
Derivative Liabilities, Gross Amount	795	520
Derivative Asset, Netting Adjustment	(334)	(532)
Derivative Liability, Netting Adjustment	(350)	(143)
Derivative Assets	1,689	986
Derivative Liability	445	377
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	79,242	73,009
Derivative Assets, Gross Amount	1,325	1,043
Derivative Liabilities, Gross Amount	250	209
Derivatives designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	71,302	64,867
Derivative Assets, Gross Amount	1,233	717
Derivative Liabilities, Gross Amount	96	207
Derivatives designated as accounting hedges | Interest rate contracts | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	33,767	34,417
Derivative Assets, Gross Amount	556	550
Derivative Liabilities, Gross Amount	78	146
Derivatives designated as accounting hedges | Interest rate contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	37,535	30,450
Derivative Assets, Gross Amount	677	167
Derivative Liabilities, Gross Amount	18	61
Derivatives designated as accounting hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	7,940	8,142
Derivative Assets, Gross Amount	92	326
Derivative Liabilities, Gross Amount	154	2
Derivatives designated as accounting hedges | Foreign exchange contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	5,395	5,580
Derivative Assets, Gross Amount	42	239
Derivative Liabilities, Gross Amount	154	2
Derivatives designated as accounting hedges | Foreign exchange contracts | Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	2,545	2,562
Derivative Assets, Gross Amount	50	87
Derivative Liabilities, Gross Amount	0	0
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	34,728	32,907
Derivative Assets, Gross Amount	698	475
Derivative Liabilities, Gross Amount	545	311
Derivatives not designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	33,864	32,025
Derivative Assets, Gross Amount	698	475
Derivative Liabilities, Gross Amount	543	307
Derivatives not designated as accounting hedges | Interest rate contracts | MSRs
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,180	1,665
Derivative Assets, Gross Amount	25	11
Derivative Liabilities, Gross Amount	13	7
Derivatives not designated as accounting hedges | Interest rate contracts | Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	30,811	28,841
Derivative Assets, Gross Amount	636	431
Derivative Liabilities, Gross Amount	511	290
Derivatives not designated as accounting hedges | Interest rate contracts | Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,873	1,519
Derivative Assets, Gross Amount	37	33
Derivative Liabilities, Gross Amount	19	10
Derivatives not designated as accounting hedges | Other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	864	882
Derivative Assets, Gross Amount	0	0
Derivative Liabilities, Gross Amount	$ 2	$ 4