Receivables Held for Investment, net - Additional Information Relating to Trouble Debt Restructuring Loan (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Average balance of TDR Loans held for investment and held for sale:
Total average balance of TDR Loans	$ 4,973	$ 9,763	$ 12,317
Interest income recognized on TDR Loans held for investment and held for sale:
Total interest income recognized on TDR Loans	368	750	877
First lien [Member]
Average balance of TDR Loans held for investment and held for sale:
Total average balance of TDR Loans	4,343	8,927	11,342
Interest income recognized on TDR Loans held for investment and held for sale:
Total interest income recognized on TDR Loans	298	665	782
Second lien [Member]
Average balance of TDR Loans held for investment and held for sale:
Total average balance of TDR Loans	630	836	975
Interest income recognized on TDR Loans held for investment and held for sale:
Total interest income recognized on TDR Loans	$ 70	$ 85	$ 95