Fair Value (Reconciliation of Recurring Fair Value Measurements) (Details) - Fair Value, Recurring [Member] - Level 3 [Member] - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	$ 4,873	$ 5,827	$ 5,395	$ 6,157
Included in earnings	(35)	(136)	(521)	(162)
Included in other comprehensive income	141	22	(115)	26
Purchases	153	255	285	349
Sales	(23)	(59)	(108)	(198)
Issuances	46	15	67	29
Settlements	(241)	(228)	(82)	(499)
Transfers Into Level 3	102	2	106	7
Transfers out of Level 3	(78)	(11)	(89)	(22)
Ending Balance	4,938	5,687	4,938	5,687
Unrealized gains/losses on assets held on Consolidated Balance Sheet	(16)	(161)	(541)	(355)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	262	298	344	333
Included in earnings	32	31	42	70
Purchases
Sales	(1)	(1)	2	3
Issuances	39	63	62	79
Settlements	(40)	(89)	(156)	(181)
Transfers into Level 3			2
Transfers out of Level 3	2
Ending Balance	296	304	296	304
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	25	22	29	64
Fair Value Additional Information [Abstract]
Net gains (losses) included in earnings (realized and unrealized) relating to Level 3 assets and liabilities	(67)	(167)	(563)	(232)
Net unrealized gains (losses) relating to Level 3 assets and liabilities	(41)	(183)	(570)	(419)
Loans Held For Sale [Member] | Residential Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	4	2	2	2
Purchases	5	1	7	2
Sales	(1)		(2)	(1)
Settlements	(3)		(3)
Transfers Into Level 3	83	1	87	4
Transfers out of Level 3		(2)	(3)	(5)
Ending Balance	88	2	88	2
Loans Held For Sale [Member] | Commercial Mortgages [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	60	73	64	87
Included in earnings		1	(1)	2
Settlements		(1)	(3)	(16)
Ending Balance	60	73	60	73
Unrealized gains/losses on assets held on Consolidated Balance Sheet		1	(1)	2
Available-for-sale Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,717	2,393	2,055	2,486
Included in earnings	14	20	32	38
Included in other comprehensive income	141	22	(115)	26
Purchases		2	4	3
Sales		(3)		(3)
Settlements	(99)	(117)	(203)	(233)
Transfers Into Level 3	19		19
Transfers out of Level 3
Ending Balance	1,792	2,317	1,792	2,317
Available-for-sale Securities [Member] | Residential Mortgage-backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,442	2,042	1,741	2,128
Included in earnings	12	18	28	36
Included in other comprehensive income	123	19	(99)	21
Settlements	(86)	(103)	(179)	(209)
Ending Balance	1,491	1,976	1,491	1,976
Available-for-sale Securities [Member] | Asset backed [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	202	266	240	274
Included in earnings	2	2	4	2
Included in other comprehensive income	16	4	(13)	6
Settlements	(10)	(11)	(21)	(21)
Ending Balance	210	261	210	261
Available-for-sale Securities [Member] | Commercial Mortgage Backed Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Transfers Into Level 3	19		19
Ending Balance	19		19
Available-for-sale Securities [Member] | Other [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	73	85	74	84
Included in other comprehensive income	2	(1)	(3)	(1)
Purchases		2	4	3
Sales		(3)		(3)
Settlements	(3)	(3)	(3)	(3)
Transfers out of Level 3
Ending Balance	72	80	72	80
Loans [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	655	272	300	272
Included in earnings	2	2	13	5
Purchases	55	13	71	33
Sales	(5)	(8)	(31)	(11)
Issuances		(1)		(1)
Settlements	(22)	(11)	340	(25)
Transfers Into Level 3		1		3
Transfers out of Level 3	(78)	(9)	(86)	(17)
Ending Balance	607	259	607	259
Unrealized gains/losses on assets held on Consolidated Balance Sheet	2	1	13	2
Equity Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	1,220	1,217	1,276	1,255
Included in earnings	(62)	4	(131)	56
Purchases	42	150	113	195
Sales	(17)	(48)	(75)	(183)
Ending Balance	1,183	1,323	1,183	1,323
Unrealized gains/losses on assets held on Consolidated Balance Sheet	(62)	3	(125)	3
Mortgage Servicing Rights [Member] | Residential Mortgage [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	605	1,131	995	1,257
Included in earnings	(40)	(156)	(419)	(262)
Purchases	43	59	61	65
Issuances	12	7	22	14
Settlements	(43)	(44)	(82)	(77)
Ending Balance	577	997	577	997
Unrealized gains/losses on assets held on Consolidated Balance Sheet	(41)	(156)	(420)	(261)
Mortgage Servicing Rights [Member] | Commercial Mortgages [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	477	681	649	726
Included in earnings	1	(55)	(166)	(88)
Purchases	4	32	23	51
Issuances	34	9	45	16
Settlements	(26)	(37)	(61)	(75)
Ending Balance	490	630	490	630
Unrealized gains/losses on assets held on Consolidated Balance Sheet	1	(55)	(166)	(88)
Trading Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance		2		2
Settlements		(2)		(2)
Derivative [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	135	56	54	25
Included in earnings	50	48	151	87
Purchases	4	(2)	6
Settlements	(48)	(16)	(70)	(26)
Ending Balance	141	86	141	86
Unrealized gains/losses on assets held on Consolidated Balance Sheet	84	45	158	(13)
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	185	230	200	268
Included in earnings	28	20	36	50
Sales	(1)	1	2	1
Settlements	(5)	(28)	(29)	(98)
Ending Balance	209	221	209	221
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	27	19	37	53
Other Assets [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance				45
Included in earnings
Settlements				(45)
Unrealized gains/losses on assets held on Consolidated Balance Sheet
Other Borrowed Funds [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	5	6	7	7
Issuances	13	12	25	26
Settlements	(16)	(13)	(30)	(28)
Ending Balance	2	5	2	5
Other liabilities [Member]
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning Balance	72	62	137	58
Included in earnings	4	11	6	20
Sales		(2)		2
Issuances	26	51	37	53
Settlements	(19)	(48)	(97)	(55)
Transfers into Level 3			2
Transfers out of Level 3	2
Ending Balance	85	78	85	78
Unrealized gains/losses on liabilities held on Consolidated Balance Sheet	$ (2)	$ 3	$ (8)	$ 11