Receivables, net - Additional Information Relating to Trouble Debt Restructuring Loan (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Average balance of TDR Loans:
Total average balance of TDR Loans	$ 7,525	$ 11,107
Interest income recognized on TDR Loans:
Total interest income recognized on TDR Loans	157	202
First lien [Member]
Average balance of TDR Loans:
Total average balance of TDR Loans	6,775	10,207
Interest income recognized on TDR Loans:
Total interest income recognized on TDR Loans	137	180
Second lien [Member]
Average balance of TDR Loans:
Total average balance of TDR Loans	750	900
Interest income recognized on TDR Loans:
Total interest income recognized on TDR Loans	$ 20	$ 22