Acquisitions and Discontinued Operations - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended			9 Months Ended			1 Months Ended	3 Months Ended						9 Months Ended
	Sep. 30, 2013 Trust	Sep. 30, 2013 Trust	Dec. 31, 2012	Sep. 30, 2012	Sep. 30, 2013 Portfolio Loans [Member] TDRs	Jun. 30, 2013 Mortgage Servicing Rights [Member]	Aug. 01, 2012 Key-Branded Credit Card [Member]	Sep. 14, 2012 New York [Member]	Sep. 30, 2012 New York [Member]	Jul. 13, 2012 New York [Member] Branch	Oct. 07, 2013 Subsequent Event [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2013 Carrying Amount [Member]	Dec. 31, 2012 Carrying Amount [Member]	Sep. 30, 2012 Carrying Amount [Member]	Sep. 30, 2013 Victory Capital Management [Member] Level 3 [Member]	Sep. 30, 2013 Segment, Discontinued Operations [Member]	Dec. 31, 2012 Segment, Discontinued Operations [Member]	Sep. 30, 2012 Segment, Discontinued Operations [Member]	Dec. 31, 2009 Segment, Discontinued Operations [Member] Trust	Sep. 30, 2013 Segment, Discontinued Operations [Member] Carrying Amount [Member]	Sep. 30, 2012 Segment, Discontinued Operations [Member] Carrying Amount [Member]	Sep. 30, 2013 Segment, Discontinued Operations [Member] Contractual Values [Member]	Sep. 30, 2013 Segment, Discontinued Operations [Member] Fair Value [Member]	Sep. 30, 2013 Maximum [Member] Mortgage Servicing Rights [Member]	Sep. 30, 2013 Maximum [Member] Segment, Discontinued Operations [Member] Carrying Amount [Member]	Sep. 30, 2012 Maximum [Member] Segment, Discontinued Operations [Member] Carrying Amount [Member]	Sep. 30, 2013 Maximum [Member] Segment, Discontinued Operations [Member] Contractual Values [Member]	Sep. 30, 2013 Maximum [Member] Segment, Discontinued Operations [Member] Fair Value [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Business acquisition intangible asset	$ 1,000,000	$ 1,000,000				$ 117,000,000			$ 40,000,000		$ 1,000,000													$ 118,000,000
Business acquisition goodwill asset	0	0							62,000,000
Acquired credit card assets							718,000,000	68,000,000
Estimated purchased credit card relationship intangible asset							135,000,000	1,000,000
Assumed reward liability							9,000,000	1,000,000
Number of retail banking branches acquired										37
Estimated fair value of the assets and deposits acquired									2,000,000,000
Loans purchased associated with branches acquired									244,000,000
Credit impaired loans purchased associated with branches acquired									25,000,000
Business acquisition premises and equipment									8,000,000
Deposits assumed associated with branches acquired in purchase and assumption agreement									2,000,000,000
Business acquisition cash received									1,800,000,000
Business acquisition, cash payment								68,000,000
Goodwill acquired								0
Investment recorded					11,000,000
Allowance for loan held as investment	868,000,000	868,000,000	888,000,000	888,000,000	1,000,000											38,000,000	55,000,000	65,000,000
Number of TDRs					1,010
Number of outstanding securitization trusts																			10
Economic interest or risk of loss associated with education loan securitization trusts																121,000,000
Fair value of loans and securities in securitization trusts after tax loss																48,000,000
Loans purchased		142,000,000
Loans at fair value	148,000,000	148,000,000	157,000,000	71,000,000								52,729,000,000	51,934,000,000	50,531,000,000
Number of outstanding securitizations trusts	2	2
Loans held by trusts with unpaid balances ninety days or more past due																						29,000,000	28,000,000
Loans held by portfolio with unpaid balances ninety days or more past due																						5,000,000	5,000,000		38,000,000	47,000,000
Loans held by the trusts with unpaid principal balances due date																90 days or more
Loans held by the portfolio with unpaid principal balances due date																90 days or more
Loans held by the trust in nonaccrual status																						12,000,000	12,000,000
Loans held by portfolio in nonaccrual status																				9,000,000	5,000,000						1,000,000	1,000,000
After tax gain on sale of subsidiary	198,000,000	92,000,000
Cash portion in gain		72,000,000
Total assets on a recurring basis at fair value															$ 31,000,000
U.S. Treasury Rate Period															7 years
Discount rate used for the Seller note															12.75%