Credit Loss Reserves - Summarizes Changes in Credit Loss Reserves by Product/Class and Related Receivable Balance by Product (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended										12 Months Ended
	Dec. 31, 2014		Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					$ 3,273					$ 4,607	$ 3,273		$ 4,607		$ 5,952
Provision for credit losses	(127)		(43)	(197)	2	(152)		(160)	267	24	(365)		(21)		2,224	[1]
Charge-offs											(854)	[2]	(1,521)	[2]	(3,021)	[2]
Recoveries											161		200		417
Total net charge-offs											(693)		(1,321)		(2,604)
Other											2		8
Reserves on receivables transferred to held for sale															(965)
Credit loss reserves at end of period	2,217					3,273					2,217		3,273		4,607
Reserve components:
Collectively evaluated for impairment	226					604					226		604		937
Individually evaluated for impairment	1,957	[3]				2,616	[3]				1,957	[3]	2,616	[3]	3,533	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	33					52					33		52		132
Receivables acquired with deteriorated credit quality	1					1					1		1		5
Total credit loss reserves	2,217					3,273					2,217		3,273		4,607
Receivables:
Collectively evaluated for impairment	11,937					14,617					11,937		14,617		18,426
Individually evaluated for impairment	10,028	[3]				11,076	[3]				10,028	[3]	11,076	[3]	12,388	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	693					879					693		879		2,109
Receivables acquired with deteriorated credit quality	12					12					12		12		16
Total receivables	22,670					26,584					22,670		26,584		32,939
First Lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					2,777					3,867	2,777		3,867		4,089
Provision for credit losses											(308)		(24)		1,812	[1]
Charge-offs											(657)	[2]	(1,186)	[2]	(2,094)	[2]
Recoveries											84		112		60
Total net charge-offs											(573)		(1,074)		(2,034)
Other											2		8
Reserves on receivables transferred to held for sale															0
Credit loss reserves at end of period	1,898					2,777					1,898		2,777		3,867
Reserve components:
Collectively evaluated for impairment	152					469					152		469		722
Individually evaluated for impairment	1,713	[3]				2,256	[3]				1,713	[3]	2,256	[3]	3,010	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	32					51					32		51		131
Receivables acquired with deteriorated credit quality	1					1					1		1		4
Total credit loss reserves	1,898					2,777					1,898		2,777		3,867
Receivables:
Collectively evaluated for impairment	10,346					12,656					10,346		12,656		16,012
Individually evaluated for impairment	9,133	[3]				10,073	[3]				9,133	[3]	10,073	[3]	11,233	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	664					830					664		830		2,043
Receivables acquired with deteriorated credit quality	10					9					10		9		13
Total receivables	20,153					23,568					20,153		23,568		29,301
Second Lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					496					740	496		740		823
Provision for credit losses											(39)		53		397	[1]
Charge-offs											(197)	[2]	(335)	[2]	(538)	[2]
Recoveries											59		38		58
Total net charge-offs											(138)		(297)		(480)
Other											0		0
Reserves on receivables transferred to held for sale															0
Credit loss reserves at end of period	319					496					319		496		740
Reserve components:
Collectively evaluated for impairment	74					135					74		135		215
Individually evaluated for impairment	244	[3]				360	[3]				244	[3]	360	[3]	523	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	1					1					1		1		1
Receivables acquired with deteriorated credit quality	0					0					0		0		1
Total credit loss reserves	319					496					319		496		740
Receivables:
Collectively evaluated for impairment	1,591					1,961					1,591		1,961		2,414
Individually evaluated for impairment	895	[3]				1,003	[3]				895	[3]	1,003	[3]	1,155	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	29					49					29		49		66
Receivables acquired with deteriorated credit quality	2					3					2		3		3
Total receivables	2,517					3,016					2,517		3,016		3,638
Personal non-credit card [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					0					0	0		0		1,040
Provision for credit losses											(18)		(50)		15	[1]
Charge-offs											0	[2]	0	[2]	(389)	[2]
Recoveries											18		50		299
Total net charge-offs											18		50		(90)
Other											0		0
Reserves on receivables transferred to held for sale															(965)
Credit loss reserves at end of period	0					0					0		0		0
Reserve components:
Collectively evaluated for impairment	0					0					0		0		0
Individually evaluated for impairment	0	[3]				0	[3]				0	[3]	0	[3]	0	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	0					0					0		0		0
Receivables acquired with deteriorated credit quality	0					0					0		0		0
Total credit loss reserves	0					0					0		0		0
Receivables:
Collectively evaluated for impairment	0					0					0		0		0
Individually evaluated for impairment	0	[3]				0	[3]				0	[3]	0	[3]	0	[3]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	0					0					0		0		0
Receivables acquired with deteriorated credit quality	0					0					0		0		0
Total receivables	$ 0					$ 0					$ 0		$ 0		$ 0

[1] Provision for credit losses during 2012 includes $112 million related to the lower of amortized cost or fair value attributable to credit for personal non-credit card receivables transferred to held for sale at June 30, 2012. See Note 7, "Receivables Held for Sale," for additional information.

[2] For collateral dependent receivables that are transferred to held for sale, existing credit loss reserves at the time of transfer are recognized as a charge-off. We transferred to held for sale certain real estate secured receivables during 2014, 2013 and 2012 that were carried at the lower of amortized cost or fair value of the collateral less cost to sell. Accordingly, we recognized the existing credit loss reserves on these receivables as additional charge-off totaling $58 million during 2014, $164 million during 2013 and $333 million during 2012.

[3] These amounts represent TDR Loans for which we evaluate reserves using a discounted cash flow methodology. Each loan is individually identified as a TDR Loan and then grouped together with other TDR Loans with similar characteristics. The discounted cash flow impairment analysis is then applied to these groups of TDR Loans. The receivable balance above excludes TDR Loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell which totaled $517 million, $604 million and $1,488 million at December 31, 2014, 2013 and 2012, respectively. The reserve component above excludes credit loss reserves for TDR Loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell which totaled $25 million, $38 million and $94 million at December 31, 2014, 2013 and 2012, respectively. These receivables and credit loss reserves are reflected within receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell in the table above.