Credit Loss Reserves - Summarizes Changes in Credit Loss Reserves by Product/Class and Related Receivable Balance by Product - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Sep. 30, 2016	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Initial lower of amortized cost or fair value adjustment		$ 541	$ 587		$ 234
Out of period adjustment to net charge-offs			(12)
Write-offs	[1]		938	[2]	2,181	[2]	$ 854
Excludes Credit loss reserves for TDR Loans that are carried at the lower of amortized cost or fair value					10		25
TDR [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Excludes TDR loans that are carried at the lower of amortized cost or fair value					250		517
Real Estate Secured Receivable Portfolio [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Write-offs			268		1,622		58
Mortgage Receivable [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Release of provision associated with a correction to the reserve calculation for a segment of the portfolio					19
Provision for Credit Losses [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Initial lower of amortized cost or fair value adjustment	[3]		$ 576		$ 234		$ 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 years ended December 31, 2016, 2015 and 2014 and, accordingly, we recognized the existing credit loss reserves on these receivables as additional charge-off totaling $268 million, $1,622 million and $58 million during the years ended December 31, 2016, 2015 and 2014, respectively.

[2] The provision for credit losses and charge-offs for real estate secured receivables during the year ended December 31, 2016 includes $576 million related to the initial lower of amortized cost or fair value adjustment attributable to credit factors for receivables transferred to held for sale. For the year ended December 31, 2015, the provision for credit losses and charge-offs included $234 million related to the initial 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. During the year ended December 31, 2016, net charge-offs dollars were impacted by an out of period adjustment which decreased net charge-offs by $12 million in order to properly reflect charge-offs for receivables which received a partial forgiveness of principal as a result of an account modification in prior periods. 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 a correction to our credit loss reserve calculation for a segment of our portfolio.

[3] Represents the portion of the initial lower of amortized cost or fair value adjustment attributable to credit factors which are recorded as provision for credit losses in the consolidated statement of income (loss).