Derivative Instruments and Hedging Activities - Notional and Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 93,966	$ 88,645
Derivative Assets, Gross Amount	1,911	1,452
Derivative Liabilities, Gross Amount	472	339
Derivative Asset, Netting Adjustment	(483)	(624)
Derivative Liability, Netting Adjustment	(181)	(164)
Derivative Assets	1,428	828
Derivative Liability	291	175
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	62,813	57,015
Derivative Assets, Gross Amount	1,335	996
Derivative Liabilities, Gross Amount	60	59
Derivatives designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	55,026	48,993
Derivative Assets, Gross Amount	1,058	702
Derivative Liabilities, Gross Amount	51	57
Derivatives designated as accounting hedges | Interest rate contracts | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	31,876	24,543
Derivative Assets, Gross Amount	706	480
Derivative Liabilities, Gross Amount	40	39
Derivatives designated as accounting hedges | Interest rate contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	23,150	24,450
Derivative Assets, Gross Amount	352	222
Derivative Liabilities, Gross Amount	11	18
Derivatives designated as accounting hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	7,787	8,022
Derivative Assets, Gross Amount	277	294
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	5,244	5,546
Derivative Assets, Gross Amount	219	221
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	2,543	2,476
Derivative Assets, Gross Amount	58	73
Derivative Liabilities, Gross Amount	0	0
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	31,153	31,630
Derivative Assets, Gross Amount	576	456
Derivative Liabilities, Gross Amount	412	280
Derivatives not designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	30,539	31,037
Derivative Assets, Gross Amount	576	456
Derivative Liabilities, Gross Amount	407	275
Derivatives not designated as accounting hedges | Interest rate contracts | MSRs
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,074	777
Derivative Assets, Gross Amount	15	10
Derivative Liabilities, Gross Amount	9	3
Derivatives not designated as accounting hedges | Interest rate contracts | Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	27,939	27,646
Derivative Assets, Gross Amount	525	413
Derivative Liabilities, Gross Amount	381	251
Derivatives not designated as accounting hedges | Interest rate contracts | Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,526	2,614
Derivative Assets, Gross Amount	36	33
Derivative Liabilities, Gross Amount	17	21
Derivatives not designated as accounting hedges | Other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	614	593
Derivative Assets, Gross Amount	0	0
Derivative Liabilities, Gross Amount	$ 5	$ 5