Portfolio Balances and Delinquency Balances Based on 90 days or more Past Due and Net Charge-Offs Related to Managed Portfolio Loans (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		$ 285,301	$ 278,197
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		2,590	2,686
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		375	494
Commercial Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		75,477	78,224
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		247	426
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		127	252
Consumer Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		67,704	65,074
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		1,832	1,707
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		240	231
Loans and Finance Receivables [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		143,181	143,298
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		2,079	2,133
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		367	483
Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	139,920	131,914
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	171	115
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		8	11
Loans [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[2]	2,200	2,985
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[2]	340	438
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		0	0
Commercial Portfolio Segment [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1],[3]	5,760	4,761
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1],[3]	0	0
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		0	0
Consumer Portfolio Segment [Member] | Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	134,160	127,153
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	171	115
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	[4]	$ 8	$ 11

[1] Excludes loans that have completed the foreclosure or short sale process (i.e., involuntary prepayments).

[2] Comprised of unsecuritized loans the Company originated and sold to private investors with servicing rights retained. Net charge-offs on these loans are not presented in the table as the data is not reported to the Company by the private investors that own these related loans.

[3] Comprised of commercial mortgages sold through Fannie Mae, Freddie Mac, and Ginnie Mae securitizations, whereby servicing has been retained by the Company.

[4] Amounts associated with $602 million and $922 million of managed securitized loans at December 31, 2017 and 2016, respectively. Net charge-off data is not reported to the Company for the remaining balance of $133.6 billion and $126.2 billion of managed securitized loans at December 31, 2017 and 2016, respectively.