Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Other Assets [Abstract]
Property and equipment at cost	$ 1,250	$ 1,064
Accumulated depreciation, property and equipment	(686)	(608)
Property and equipment, net	564	456
Nonmarketable equity securities	1,410	1,233
Restricted cash collections for securitization trusts	965	923
Investments in qualified affordable housing projects	649	472
Accrued interest, late fees, and rent receivables	599	550
Deferred tax assets, net	317	461
Equity method investments	262	220
Goodwill	240	240
Other accounts receivable	203	116
Restricted cash and cash equivalents	124	94
Derivative contracts in a receivable position, fair value	41	39
Cash collateral placed with counterparties	26	29
Other assets, other	753	830
Total other assets	6,153	5,663
Federal Home Loan Bank stock	903	745
Federal Reserve Bank stock	448	445
Equity securities without a readily determinable fair value	59
Impairment related to equity securities without a readily determinable fair value	2
Investments in qualified affordable housing projects, unfunded commitment	319	240
Goodwill [Line Items]
Goodwill	240	240
Insurance operations
Other Assets [Abstract]
Goodwill	27	27
Goodwill [Line Items]
Goodwill	27	27
Automotive Finance operations
Other Assets [Abstract]
Goodwill	20	20
Goodwill [Line Items]
Goodwill	20	20
Corporate and Other
Other Assets [Abstract]
Goodwill	193	193
Goodwill [Line Items]
Goodwill	$ 193	$ 193