Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions		3 Months Ended		12 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 15, 2016	Jun. 30, 2015
Bank Servicing Fees		$ 58	$ 62
Principal Amount Outstanding of Loans Serviced	[1]	28,700		$ 27,700
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		284,670		278,197
Principal Amount Outstanding of Loans Serviced For Third Parties		23,700		22,900
Servicing Asset at Fair Value, Amount		1,645		1,572
Mortgage Servicing Rights, Fair Value [Member]
Bank Servicing Fees		101	87
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		164,500		160,200
Principal Amount Outstanding of Loans Serviced For Third Parties		135,600		129,600
Unpaid Principal Balance of Outstanding Underlying MSRs Purchased		0	8,100
Principal Amount Sold on Loans Serviced for Third Parties		64	221
Servicing Asset at Fair Value, Amount		1,645	1,182	1,572	$ 1,307
Asset-backed Securities, Securitized Loans and Receivables [Member]
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement	[1]	138,313		131,914
indirect auto loan servicing rights [Member]
Bank Servicing Fees		1	2
Servicing Asset							$ 13
Servicing Asset at Fair Value, Amount		3		4
Commercial Mortgage Servicing Rights [Member]
Servicing Asset at Amortized Cost		63		62
Bank Servicing Fees		5	0
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		5,000		4,800
Servicing Asset at Fair Value, Amount		65		$ 62
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		$ 62				$ 62
Finite-Lived Intangible Asset, Useful Life		7 years		7 years
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]	$ 448		$ 512
Proceeds from Securitizations of Consumer Loans					$ 1,000
Pillar Financial [Member]
Bank Servicing Fees		$ 4	$ 0

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