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				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period	$ 2,692		$ 4,098		$ 3,273		$ 4,607
Provision for credit losses	(43)		(160)		(238)		131
Charge-offs	(211)	[1]	(284)	[1]	(716)	[1]	(1,210)	[1]
Recoveries	25		43		144		161
Total net charge-offs	(186)		(241)		(572)		(1,049)
Other							8
Credit loss reserves at end of period	2,463		3,697		2,463		3,697
Reserve components:
Collectively evaluated for impairment	291		742		291		742
Individually evaluated for impairment	2,135	[2]	2,902	[2]	2,135	[2]	2,902	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	35		52		35		52
Receivables acquired with deteriorated credit quality	2		1		2		1
Total credit loss reserves	2,463		3,697		2,463		3,697
Receivables:
Collectively evaluated for impairment	12,557		15,517		12,557		15,517
Individually evaluated for impairment	10,246	[2]	11,431	[2]	10,246	[2]	11,431	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	690		883		690		883
Receivables acquired with deteriorated credit quality	10		13		10		13
Total receivables	23,503		27,844		23,503		27,844
First Lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period	2,296		3,463		2,777		3,867
Provision for credit losses	(45)		(145)		(184)		121
Charge-offs	(168)	[1]	(212)	[1]	(559)	[1]	(950)	[1]
Recoveries	20		27		69		87
Total net charge-offs	(148)		(185)		(490)		(863)
Other							8
Credit loss reserves at end of period	2,103		3,133		2,103		3,133
Reserve components:
Collectively evaluated for impairment	201		591		201		591
Individually evaluated for impairment	1,865	[2]	2,490	[2]	1,865	[2]	2,490	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	35		51		35		51
Receivables acquired with deteriorated credit quality	2		1		2		1
Total credit loss reserves	2,103		3,133		2,103		3,133
Receivables:
Collectively evaluated for impairment	10,839		13,475		10,839		13,475
Individually evaluated for impairment	9,326	[2]	10,362	[2]	9,326	[2]	10,362	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	662		835		662		835
Receivables acquired with deteriorated credit quality	8		10		8		10
Total receivables	20,835		24,682		20,835		24,682		23,568
Second Lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period	396		635		496		740
Provision for credit losses	3		(8)		(36)		54
Charge-offs	(43)	[1]	(72)	[1]	(157)	[1]	(260)	[1]
Recoveries	4		9		57		30
Total net charge-offs	(39)		(63)		(100)		(230)
Other							0
Credit loss reserves at end of period	360		564		360		564
Reserve components:
Collectively evaluated for impairment	90		151		90		151
Individually evaluated for impairment	270	[2]	412	[2]	270	[2]	412	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	0		1		0		1
Receivables acquired with deteriorated credit quality	0		0		0		0
Total credit loss reserves	360		564		360		564
Receivables:
Collectively evaluated for impairment	1,718		2,042		1,718		2,042
Individually evaluated for impairment	920	[2]	1,069	[2]	920	[2]	1,069	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	28		48		28		48
Receivables acquired with deteriorated credit quality	2		3		2		3
Total receivables	2,668		3,162		2,668		3,162		3,016
Personal non-credit card [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period	0		0		0		0
Provision for credit losses	(1)		(7)		(18)		(44)
Charge-offs	0	[1]	0	[1]	0	[1]	0	[1]
Recoveries	1		7		18		44
Total net charge-offs	1		7		18		44
Other							0
Credit loss reserves at end of period	0		0		0		0
Reserve components:
Collectively evaluated for impairment	0		0		0		0
Individually evaluated for impairment	0	[2]	0	[2]	0	[2]	0	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	0		0		0		0
Receivables acquired with deteriorated credit quality	0		0		0		0
Total credit loss reserves	0		0		0		0
Receivables:
Collectively evaluated for impairment	0		0		0		0
Individually evaluated for impairment	0	[2]	0	[2]	0	[2]	0	[2]
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell	0		0		0		0
Receivables acquired with deteriorated credit quality	0		0		0		0
Total receivables	$ 0		$ 0		$ 0		$ 0

[1] 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 the three and nine months ended September 30, 2014 and 2013 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 $12 million and $50 million during the three and nine months ended September 30, 2014, respectively, compared with $21 million and $140 million during the three and nine months ended September 30, 2013

[2] 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 $509 million and $637 million at September 30, 2014 and 2013, 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 $26 million and $36 million at September 30, 2014 and 2013, respectively. These 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.