Fair Value (Reconciliation of Recurring Fair Value Measurements) (Details) - Fair Value, Measurements, Recurring [Member] - Level 3 [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 8,606	$ 9,788
Included in earnings	(162)	96
Included in other comprehensive income	(60)	(11)
Purchases	116	179
Sales	(677)	(1,104)
Issuances	667	1,114
Settlements	(445)	(406)
Transfers Into Level 3	2	6
Transfers Out of Level 3	(18)	(26)
Ending Balance	8,029	9,636
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(201)	27
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	495	716
Included in earnings	7	42
Sales	2
Issuances	61	25
Settlements	(210)	(73)
Ending Balance	355	710
Unrealized gains or (losses) on liabilities held on Consolidated Balance Sheet	8	(6)
Fair Value Additional Information [Abstract]
Net gains (losses) included in earnings (realized and unrealized) relating to Level 3 assets and liabilities	(169)	54
Net unrealized gains (losses) relating to Level 3 assets and liabilities	(209)	33
Available-for-sale Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,535	5,525
Included in earnings	25	39
Included in other comprehensive income	(58)	(11)
Purchases	2	3
Sales	(2)
Settlements	(197)	(218)
Ending Balance	4,305	5,338
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(1)	(1)
Available-for-sale Securities [Member] | Residential mortgage-backed Securities [Member] | Mortgage-backed Securities Non-agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4,008	4,798
Included in earnings	22	25
Included in other comprehensive income	(45)	(14)
Settlements	(175)	(185)
Ending Balance	3,810	4,624
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(1)	(1)
Available-for-sale Securities [Member] | Commercial mortgage-backed securities [Member] | Mortgage-backed Securities Non-agency [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Included in earnings		7
Settlements		(7)
Available-for-sale Securities [Member] | Asset backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	482	563
Included in earnings	3	6
Included in other comprehensive income	(12)	4
Settlements	(22)	(25)
Ending Balance	451	548
Available-for-sale Securities [Member] | State and Municipal [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	15	134
Included in other comprehensive income	(1)	(1)
Ending Balance	14	133
Available-for-sale Securities [Member] | Other debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	30	30
Included in earnings		1
Purchases	2	3
Sales	(2)
Settlements		(1)
Ending Balance	30	33
Financial Derivatives [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	31	42
Included in earnings	34	71
Purchases		1
Settlements	(24)	(60)
Ending Balance	41	54
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	28	59
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	473	526
Included in earnings	7	41
Sales	2
Settlements	(149)	(38)
Ending Balance	333	529
Unrealized gains or (losses) on liabilities held on Consolidated Balance Sheet	8	(6)
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	5	6
Purchases	3	6
Sales	(1)
Transfers Into Level 3	2	1
Transfers Out of Level 3	(5)	(6)
Ending Balance	4	7
Loans Held For Sale [Member] | Commercial Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	641	893
Included in earnings	16	21
Sales	(649)	(1,020)
Issuances	647	1,083
Settlements		(2)
Ending Balance	655	975
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	12	15
Trading Securities - Debt [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	3	32
Settlements	(1)	(29)
Ending Balance	2	3
Mortgage Servicing Rights [Member] | Residential Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,063	845
Included in earnings	(226)	(67)
Purchases	52	83
Issuances	11	17
Settlements	(37)	(39)
Ending Balance	863	839
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(225)	(65)
Mortgage Servicing Rights [Member] | Commercial Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	526	506
Included in earnings	(55)	(16)
Purchases	3	11
Issuances	9	14
Settlements	(23)	(21)
Ending Balance	460	494
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(55)	(16)
Equity Investments [Member] | Direct equity investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,098	1,152
Included in earnings	51	29
Purchases	23	43
Sales	(16)	(75)
Ending Balance	1,156	1,149
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	50	18
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	340	397
Included in earnings	2	10
Purchases	33	32
Sales	(8)	(4)
Settlements	(25)	(37)
Transfers Into Level 3		5
Transfers Out of Level 3	(13)	(20)
Ending Balance	329	383
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	1	8
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	364	390
Included in earnings	(9)	9
Included in other comprehensive income	(2)
Sales	(1)	(5)
Settlements	(138)
Ending Balance	214	394
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(11)	9
Other Assets [Member] | BlackRock Series C Preferred Stock
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	357	375
Included in earnings	(11)	9
Settlements	(138)
Ending Balance	208	384
Unrealized gains or (losses) on assets held on Consolidated Balance Sheet	(11)	9
Other Assets [Member] | Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	7	15
Included in earnings	2
Included in other comprehensive income	(2)
Sales	(1)	(5)
Ending Balance	6	10
Other Borrowed Funds [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	12	181
Issuances	23	25
Settlements	(27)	(35)
Ending Balance	8	171
Other Liabilities
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	10	9
Included in earnings		1
Issuances	38
Settlements	(34)
Ending Balance	$ 14	$ 10