Derivative Instruments and Hedging Activities - Notional and Fair Values of Derivative Instruments (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	$ 155,083	$ 142,938
Derivative Assets, Gross Amount	1,069	1,494
Derivative Liabilities, Gross Amount	1,531	1,438
Derivative Asset, Netting Adjustment	(375)	(539)
Derivative Liability, Netting Adjustment	(246)	(336)
Derivative Assets	694	955
Derivative Liability	1,285	1,102
Derivatives designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	108,051	98,896
Derivative Assets, Gross Amount	395	717
Derivative Liabilities, Gross Amount	1,064	865
Derivatives designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	100,209	90,880
Derivative Assets, Gross Amount	306	446
Derivative Liabilities, Gross Amount	1,006	856
Derivatives designated as accounting hedges | Interest rate contracts | Fair value hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	48,009	40,480
Derivative Assets, Gross Amount	246	295
Derivative Liabilities, Gross Amount	637	569
Derivatives designated as accounting hedges | Interest rate contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	52,200	50,400
Derivative Assets, Gross Amount	60	151
Derivative Liabilities, Gross Amount	369	287
Derivatives designated as accounting hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	7,842	8,016
Derivative Assets, Gross Amount	89	271
Derivative Liabilities, Gross Amount	58	9
Derivatives designated as accounting hedges | Foreign exchange contracts | Cash flow hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	5,307	5,620
Derivative Assets, Gross Amount	27	108
Derivative Liabilities, Gross Amount	34	9
Derivatives designated as accounting hedges | Foreign exchange contracts | Net investment hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	2,535	2,396
Derivative Assets, Gross Amount	62	163
Derivative Liabilities, Gross Amount	24	0
Derivatives not designated as accounting hedges
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	47,032	44,042
Derivative Assets, Gross Amount	674	777
Derivative Liabilities, Gross Amount	467	573
Derivatives not designated as accounting hedges | Interest rate contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	45,280	42,275
Derivative Assets, Gross Amount	623	720
Derivative Liabilities, Gross Amount	460	559
Derivatives not designated as accounting hedges | Interest rate contracts | MSRs
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,551	1,696
Derivative Assets, Gross Amount	20	17
Derivative Liabilities, Gross Amount	13	21
Derivatives not designated as accounting hedges | Interest rate contracts | Customer accommodation
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	41,220	39,474
Derivative Assets, Gross Amount	571	670
Derivative Liabilities, Gross Amount	435	530
Derivatives not designated as accounting hedges | Interest rate contracts | Other interest rate exposures
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	2,509	1,105
Derivative Assets, Gross Amount	32	33
Derivative Liabilities, Gross Amount	12	8
Derivatives not designated as accounting hedges | Other contracts
Derivatives, Fair Value [Line Items]
Notional or Contractual Amount	1,752	1,767
Derivative Assets, Gross Amount	51	57
Derivative Liabilities, Gross Amount	$ 7	$ 14