Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Dec. 31, 2013
Bank Servicing Fees		$ 40	$ 44	$ 113	$ 143
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	256,461		256,461			$ 248,646
Servicing Asset at Fair Value, Amount		1,262		1,262			1,206
Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	118,663		118,663			110,591
Mortgage Servicing Rights, Fair Value [Member]
Bank Servicing Fees		89	81	254	241
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		149,200		149,200			142,100
Principal Amount Outstanding of Loans Serviced For Third Parties		122,000		122,000			115,500
Unpaid Principal Balance of Outstanding Underlying MSRs Purchased				10,300	9,000
Unpaid Principal Balance of Outstanding Underlying MSRs Transferred				10,300
Principal Amount Sold on Loans Serviced for Third Parties				590	612
Servicing Asset at Fair Value, Amount		1,262	1,305	1,262	1,305		1,206	$ 1,300
indirect auto loan servicing rights [Member]
Bank Servicing Fees		2	$ 0	3	$ 0
Servicing Asset						$ 13
Servicing Asset at Fair Value, Amount		11		11
Servicing Asset at Amortized Cost		11		11
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]	$ 889		889			$ 0
Proceeds from Securitizations of Consumer Loans				$ 1,000

[1] Excludes $2.0 billion and $3.2 billion of LHFS at September 30, 2015 and December 31, 2014, respectively.