Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Aug. 01, 2016	Jun. 01, 2016
Other Assets [Abstract]
Property, Plant and Equipment, Gross	$ 1,064	$ 901
Accumulated Depreciation, Depletion and Amortization, Property Plant and Equipment	(608)	(525)
Property, Plant and Equipment, Net	456	376
Nonmarketable equity securities	1,233	1,046
Restricted cash collections for securitization trusts	812	1,694
Interest Receivable	550	476
Deferred Tax Assets, Net	461	994
Goodwill	240	240
Accounts and Other Receivables, Net, Current	116	100
Cash reserve deposits held for securitization trusts	111	184
Restricted Cash and Cash Equivalents	94	111
Derivative Asset, Fair Value, Gross Asset	39	95
Cash and securities collateral placed with counterparties	29	167
Other Assets, Miscellaneous	1,522	1,371
Other Assets	5,663	6,854
Federal Home Loan Bank Stock	745	577
Federal Reserve Bank Stock	445	435
Goodwill [Line Items]
Goodwill	240	240
Insurance Operations Member
Other Assets [Abstract]
Goodwill	27	27
Goodwill [Line Items]
Goodwill	27	27
Corporate and Other [Member]
Other Assets [Abstract]
Goodwill	193	193		$ 193
Goodwill [Line Items]
Goodwill	193	193		$ 193
Automotive Finance Operations [Member]
Other Assets [Abstract]
Goodwill	20	20	$ 20
Goodwill [Line Items]
Goodwill	$ 20	$ 20	$ 20