Credit Loss Reserves - Summarizes Changes in Credit Loss Reserves by Product/Class and Related Receivable Balance by Product (Detail) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					$ 2,217				$ 3,273	$ 2,217		$ 3,273	$ 4,607
Provision for credit losses		$ 13	$ 18	$ 192	27	$ (127)	$ (43)	$ (197)	2	250	[1]	(365)	(21)
Charge-offs	[2]									(2,181)	[1]	(854)	(1,521)
Recoveries										25		161	200
Total net charge-offs										(2,156)		(693)	(1,321)
Other												2
Credit loss reserves at end of period		311				2,217				311		2,217	3,273
Reserve components:
Collectively evaluated for impairment														$ 79	$ 226	$ 604
Individually evaluated for impairment	[3]													220	1,957	2,616
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														12	33	52
Receivables acquired with deteriorated credit quality														311	2,217
Total credit loss reserves		311			2,217	2,217			3,273	2,217		3,273	4,607	311	2,217	3,273
Receivables:
Collectively evaluated for impairment														7,553	11,937	14,617
Individually evaluated for impairment	[3]													1,272	10,028	11,076
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														326	693	879
Total receivables														9,156	22,670	26,584
Allowance For Loan And Lease Losses, Charge Offs Upon Transfer To Held For Sale													8
First lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					1,898				2,777	1,898		2,777	3,867
Provision for credit losses										223	[1]	(308)	(24)
Charge-offs	[2]									(2,004)	[1]	(657)	(1,186)
Recoveries										20		84	112
Total net charge-offs										(1,984)		(573)	(1,074)
Other												2
Credit loss reserves at end of period		137				1,898				137		1,898	2,777
Reserve components:
Collectively evaluated for impairment														40	152	469
Individually evaluated for impairment	[3]													85	1,713	2,256
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														12	32	51
Total credit loss reserves		137			1,898	1,898			2,777	1,898		2,777	3,867	137	1,898	2,777
Receivables:
Collectively evaluated for impairment														6,359	10,346	12,656
Individually evaluated for impairment	[3]													640	9,133	10,073
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														299	664	830
Total receivables														7,302	20,153	23,568
Allowance For Loan And Lease Losses, Charge Offs Upon Transfer To Held For Sale													8
Second lien [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					319				496	319		496	740
Provision for credit losses										27	[1]	(39)	53
Charge-offs	[2]									(177)	[1]	(197)	(335)
Recoveries										5		59	38
Total net charge-offs										(172)		(138)	(297)
Other												0
Credit loss reserves at end of period		174				319				174		319	496
Reserve components:
Collectively evaluated for impairment														39	74	135
Individually evaluated for impairment	[3]													135	244	360
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														0	1	1
Total credit loss reserves		174			319	319			496	319		496	740	174	319	496
Receivables:
Collectively evaluated for impairment														1,194	1,591	1,961
Individually evaluated for impairment	[3]													632	895	1,003
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														27	29	49
Total receivables														1,854	2,517	3,016
Allowance For Loan And Lease Losses, Charge Offs Upon Transfer To Held For Sale													0
Personal non-credit card [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Credit loss reserves at beginning of period					0				0	0		0	0
Provision for credit losses										0	[1]	(18)	(50)
Charge-offs	[2]									0	[1]	0	0
Recoveries										0		18	50
Total net charge-offs										0		18	50
Other												0
Credit loss reserves at end of period		0				0				0		0	0
Reserve components:
Collectively evaluated for impairment														0	0	0
Individually evaluated for impairment	[3]													0	0	0
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														0	0	0
Total credit loss reserves		$ 0			$ 0	$ 0			$ 0	$ 0		$ 0	0	0	0	0
Receivables:
Collectively evaluated for impairment														0	0	0
Individually evaluated for impairment	[3]													0	0	0
Receivables carried at the lower of amortized cost or fair value of the collateral less cost to sell														0	0	0
Total receivables														0	0	0
Allowance For Loan And Lease Losses, Charge Offs Upon Transfer To Held For Sale													$ 0
Receivables Acquired with Deteriorated Credit Quality [Member]
Reserve components:
Receivables acquired with deteriorated credit quality														0	1	1
Receivables:
Receivables acquired with deteriorated credit quality														5	12	12
Receivables Acquired with Deteriorated Credit Quality [Member] | First lien [Member]
Reserve components:
Receivables acquired with deteriorated credit quality														0	1	1
Receivables:
Receivables acquired with deteriorated credit quality														4	10	9
Receivables Acquired with Deteriorated Credit Quality [Member] | Second lien [Member]
Reserve components:
Receivables acquired with deteriorated credit quality														0	0	0
Receivables:
Receivables acquired with deteriorated credit quality														1	2	3
Receivables Acquired with Deteriorated Credit Quality [Member] | Personal non-credit card [Member]
Reserve components:
Receivables acquired with deteriorated credit quality														0	0	0
Receivables:
Receivables acquired with deteriorated credit quality														$ 0	$ 0	$ 0

[1] The provision for credit losses and charge-offs for real estate secured receivables during the year ended December 31, 2015 includes $234 million related to the lower of amortized cost or fair value adjustment attributable to credit factors for receivables transferred to held for sale. See Note 7, "Receivables Held for Sale," for additional information. The provision for credit losses for real estate secured receivables during the year ended December 31, 2015 was impacted by a release of approximately $19 million associated with an out of period adjustment to our credit loss reserve calculation for a segment of our portfolio.

[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 the years ended December 31, 2015, 2014 and 2013 and, accordingly, we recognized the existing credit loss reserves on these receivables as additional charge-off totaling $1,622 million during the year ended December 31, 2015 compared with $58 million and $164 million during the years ended December 31, 2014 and 2013, respectively.

[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 $250 million, $517 million and $604 million at December 31, 2015, 2014 and 2013, respectively. The reserve component above excludes credit loss reserves totaling $10 million, $25 million and $38 million at December 31, 2015, 2014 and 2013, respectively, for TDR Loans that are carried at the lower of amortized cost or fair value of the collateral less cost to sell. These receivables and credit loss reserves are reflected within receivables and credit loss reserves carried at the lower of amortized cost or fair value of the collateral less cost to sell in the table above.