Other Assets (Schedule of Other Assets) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Aug. 01, 2016	Jun. 01, 2016
Goodwill [Line Items]
Goodwill	$ 240	$ 240
Property, Plant and Equipment, Gross	1,024	901
Accumulated depreciation	(587)	(525)
Property, Plant and Equipment, Net	437	376
Restricted cash collections for securitization trusts	1,260	1,694
Nonmarketable equity securities	1,065	1,046
Deferred Tax Assets, Net	659	994
Interest Receivable	508	476
Goodwill	240	240
Accounts and Other Receivables, Net, Current	212	100
Cash reserve deposits held for securitization trusts	120	184
Restricted Cash and Cash Equivalents	112	111
Derivative Asset, Fair Value, Gross Asset	37	95
Cash and securities collateral placed with counterparties	20	167
Other Assets, Miscellaneous	1,393	1,371
Other Assets	6,063	6,854
Federal Home Loan Bank Stock	581	577
Federal Reserve Bank Stock	445	435
Insurance Operations Member
Goodwill [Line Items]
Goodwill	27	27
Goodwill	27	27
Corporate and Other [Member]
Goodwill [Line Items]
Goodwill	193	193		$ 193
Goodwill	193	193		$ 193
Automotive Finance Operations [Member]
Goodwill [Line Items]
Goodwill	20	20	$ 20
Goodwill	$ 20	$ 20	$ 20