Goodwill and Intangible Assets - Additional Information (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 15, 2016
Bank Servicing Fees		$ 191	$ 189	$ 169
Principal Amount Outstanding of Loans Serviced		30,100	27,700
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		285,301	278,197
Mortgage Servicing Rights, Fair Value [Member]
Bank Servicing Fees		403	366	347
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		165,500	160,200
Principal Amount Outstanding of Loans Serviced For Third Parties		136,100	129,600
Unpaid Principal Balance of Outstanding Underlying MSRs Purchased		0	19,700
Principal Amount Sold on Loans Serviced for Third Parties		1,100	575
Servicing Asset at Fair Value, Amount		1,710	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]	139,920	131,914
Commercial Mortgage Servicing Rights [Member]
Servicing Asset at Amortized Cost		65	62
Bank Servicing Fees		22	0	0
Principal Amount Outstanding on Loans Managed and Securitized or Asset-backed Financing Arrangement		5,800	4,800
Servicing Asset at Fair Value, Amount		75	62
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets					$ 62
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
Pillar Financial [Member]
Bank Servicing Fees		14	0	$ 0
Principal Amount Outstanding of Loans Serviced For Third Parties		$ 24,300	$ 22,900

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