Business Segment Information (Market Segment Financial Results) (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Net interest income (expense)		$ 513	$ 606
Provision for credit losses		411	(13)
Noninterest income		237	238
Noninterest expenses		425	433
(Benefit) provision for income taxes		(21)	85
Net (loss) income		(65)	339
Net credit-related charge-offs (recoveries)		84	11
Assets, average		73,265	69,771
Loans, average		49,604	49,677
Deposits, average		$ 56,768	$ 53,996
Return on average assets	[1]	(0.35%)	1.97%
Efficiency ratio	[2]	56.57%	50.81%
Michigan
Net interest income (expense)		$ 163	$ 187
Provision for credit losses		24	5
Noninterest income		72	72
Noninterest expenses		140	139
(Benefit) provision for income taxes		15	26
Net (loss) income		56	89
Net credit-related charge-offs (recoveries)		3	4
Assets, average		12,899	13,075
Loans, average		12,191	12,557
Deposits, average		$ 20,748	$ 19,893
Return on average assets	[1]	1.05%	1.76%
Efficiency ratio	[2]	58.91%	53.66%
California
Net interest income (expense)		$ 182	$ 205
Provision for credit losses		51	(1)
Noninterest income		36	40
Noninterest expenses		98	100
(Benefit) provision for income taxes		17	37
Net (loss) income		52	109
Net credit-related charge-offs (recoveries)		11	(3)
Assets, average		18,377	18,934
Loans, average		18,027	18,652
Deposits, average		$ 17,466	$ 16,238
Return on average assets	[1]	1.12%	2.33%
Efficiency ratio	[2]	44.99%	40.91%
Texas
Net interest income (expense)		$ 115	$ 122
Provision for credit losses		290	(11)
Noninterest income		30	32
Noninterest expenses		84	84
(Benefit) provision for income taxes		(50)	19
Net (loss) income		(179)	62
Net credit-related charge-offs (recoveries)		70	13
Assets, average		11,154	10,911
Loans, average		10,566	10,262
Deposits, average		$ 9,204	$ 8,697
Return on average assets	[1]	(6.45%)	2.31%
Efficiency ratio	[2]	58.25%	54.62%
Other Markets
Net interest income (expense)		$ 86	$ 92
Provision for credit losses		46	(8)
Noninterest income		87	87
Noninterest expenses		93	92
(Benefit) provision for income taxes		4	19
Net (loss) income		30	76
Net credit-related charge-offs (recoveries)		0	(3)
Assets, average		9,766	8,975
Loans, average		8,820	8,206
Deposits, average		$ 8,032	$ 7,906
Return on average assets	[1]	1.24%	3.41%
Efficiency ratio	[2]	53.76%	51.28%
Finance & Other
Net interest income (expense)		$ (33)	$ 0
Provision for credit losses		0	2
Noninterest income		12	7
Noninterest expenses		10	18
(Benefit) provision for income taxes	[3]	(7)	(16)
Net (loss) income		(24)	3
Net credit-related charge-offs (recoveries)		0	0
Assets, average		21,069	17,876
Loans, average		0	0
Deposits, average		$ 1,318	$ 1,262

[1] Return on average assets is calculated based on the greater of average assets or average liabilities and attributed equity.

[2] Noninterest expenses as a percentage of the sum of net interest income and noninterest income excluding net (losses) gains from securities and a derivative contract tied to the conversion rate of Visa Class B shares.

[3] Included discrete tax benefits of $3 million and $11 million for the three months ended March 31, 2020 and 2019, respectively.