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		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		$ 291,364		$ 291,364		$ 285,301
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		2,583		2,583		2,590
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		74	$ 71	155	$ 186
Commercial Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		77,101		77,101		75,477
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		355		355		247
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		17	19	34	68
Consumer Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		67,834		67,834		67,704
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		1,642		1,642		1,832
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		56	51	118	114
Loans and Finance Receivables [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		144,935		144,935		143,181
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		1,997		1,997		2,079
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		73	70	152	182
Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		144,479		144,479		139,920
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		295		295		171
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		1	1	3	4
Loans [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	1,950		1,950		2,200
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	291		291		340
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		0	0	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	[2]	5,894		5,894		5,760
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[2]	0		0		0
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		0	0	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		138,585		138,585		134,160
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		295		295		$ 171
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	[3]	$ 1	$ 1	$ 3	$ 4

[1] 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.

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

[3] Amounts associated with $482 million and $602 million of managed securitized loans at June 30, 2018 and December 31, 2017, respectively. Net charge-off data is not reported to the Company for the remaining balance of $138.1 billion and $133.6 billion of managed securitized loans at June 30, 2018 and December 31, 2017, respectively.