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		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		$ 293,381		$ 293,381		$ 285,301
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		2,593		2,593		2,590
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		89	$ 81	245	$ 268
Commercial Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		77,958		77,958		75,477
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		310		310		247
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		42	22	76	90
Consumer Portfolio Segment [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		69,257		69,257		67,704
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		1,867		1,867		1,832
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		46	56	164	171
Loans and Finance Receivables [Member]
Principal Amount Outstanding of Loans Held-in-portfolio		147,215		147,215		143,181
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		2,177		2,177		2,079
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		88	78	240	261
Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		144,786		144,786		139,920
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		226		226		171
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement		1	3	5	7
Loans [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	1,380		1,380		2,200
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	190		190		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]	6,039		6,039		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		138,747		138,747		134,160
Delinquent Amount at End of Period on Loans Managed and Securitized or Asset-backed Financing Arrangement		226		226		$ 171
Net Credit Losses During Period on Loans Managed or Securitized or Asset-backed Financing Arrangement	[3]	$ 1	$ 3	$ 5	$ 7

[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 $429 million and $602 million of managed securitized loans at September 30, 2018 and December 31, 2017, respectively. Net charge-off data is not reported to the Company for the remaining balance of $138.3 billion and $133.6 billion of managed securitized loans at September 30, 2018 and December 31, 2017, respectively.