Business Segment Information (Market Segment Financial Results) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Net interest income (expense) (FTE)									$ 1,731		$ 1,657		$ 1,651
Provision for credit losses	16	22	19	22	18	35	45	46	79		144		478
Noninterest income									818		792		789
Noninterest expenses	427	449	433	448	479	463	411	418	1,757		1,771		1,642
Provision (benefit) for income taxes (FTE)									192		141		60
Income from discontinued operations, net of tax									0		0		17
Net income (loss)	130	117	144	130	96	98	96	103	521		393		277
Net credit-related charge-offs									170		328		564
Assets, average	62,855				56,917				62,855		56,917		55,553
Loans, average									43,306		40,075		40,517
Deposits, average									49,540		43,762		39,486
Return on average assets									0.83%	[1]	0.69%	[1]	0.50%	[1]
Efficiency ratio									69.24%		72.73%		67.39%
Michigan
Net interest income (expense) (FTE)									780		808		816
Provision for credit losses									4		84		197
Noninterest income									387		381		397
Noninterest expenses									716		745		757
Provision (benefit) for income taxes (FTE)									159		133		92
Income from discontinued operations, net of tax													0
Net income (loss)									288		227		167
Net credit-related charge-offs									41		148		211
Assets, average	13,922				14,164				13,922		14,164		14,692
Loans, average									13,618		13,937		14,510
Deposits, average									19,573		18,536		17,697
Return on average assets									1.40%	[1]	1.16%	[1]	0.88%	[1]
Efficiency ratio									61.27%		62.34%		62.13%
California
Net interest income (expense) (FTE)									701		654		627
Provision for credit losses									3		21		131
Noninterest income									136		136		133
Noninterest expenses									394		405		409
Provision (benefit) for income taxes (FTE)									167		134		89
Income from discontinued operations, net of tax													0
Net income (loss)									273		230		131
Net credit-related charge-offs									47		75		193
Assets, average	12,979				12,014				12,979		12,014		12,516
Loans, average									12,736		11,819		12,337
Deposits, average									14,568		12,667		11,892
Return on average assets									1.76%	[1]	1.69%	[1]	1.00%	[1]
Efficiency ratio									47.11%		51.21%		53.77%
Texas
Net interest income (expense) (FTE)									570		477		318
Provision for credit losses									40		2		48
Noninterest income									124		103		91
Noninterest expenses									360		294		253
Provision (benefit) for income taxes (FTE)									104		103		38
Income from discontinued operations, net of tax													0
Net income (loss)									190		181		70
Net credit-related charge-offs									22		17		47
Assets, average	10,309				8,092				10,309		8,092		6,687
Loans, average									9,552		7,705		6,480
Deposits, average									10,040		7,805		5,320
Return on average assets									1.69%	[1]	2.12%	[1]	1.04%	[1]
Efficiency ratio									51.87%		50.64%		61.92%
Other Markets
Net interest income (expense) (FTE)									322		302		310
Provision for credit losses									31		39		100
Noninterest income									103		94		96
Noninterest expenses									175		204		190
Provision (benefit) for income taxes (FTE)									14		3		(11)
Income from discontinued operations, net of tax													0
Net income (loss)									205		150		127
Net credit-related charge-offs									60		88		113
Assets, average	7,871				6,955				7,871		6,955		7,507
Loans, average									7,400		6,614		7,190
Deposits, average									4,959		4,394		3,828
Return on average assets									2.61%	[1]	2.14%	[1]	1.70%	[1]
Efficiency ratio									42.49%		52.77%		47.79%
Finance & Other
Net interest income (expense) (FTE)									(642)		(584)		(420)
Provision for credit losses									1		(2)		2
Noninterest income									68		78		72
Noninterest expenses									112		123		33
Provision (benefit) for income taxes (FTE)									(252)		(232)		(148)
Income from discontinued operations, net of tax													17
Net income (loss)									(435)		(395)		(218)
Net credit-related charge-offs									0		0		0
Assets, average	17,774				15,692				17,774		15,692		14,151
Loans, average									0		0		0
Deposits, average									$ 400		$ 360		$ 749

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