Segment and Geographic Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 976	$ 996	$ 984	$ 951	$ 983	$ 970	$ 916	$ 850	$ 3,907	$ 3,719	$ 3,375
Nonoperating Income (Expense)	392	388	374	376	356	332	211	243	1,530	1,142	1,276
Revenues									5,437	4,861	4,651
Provision for Loan Losses Expensed	267	258	172	220	240	211	140	116	917	707	457
Noninterest Expense	721	735	773	710	668	674	724	695	2,939	2,761	2,948
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	380	$ 391	$ 413	$ 397	431	$ 417	$ 263	$ 282	1,581	1,393	1,246
Assets	163,728				158,581				163,728	158,581	151,631
Net Interest Income (Loss) after Provision for Loan Losses										3,012	2,918
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue									3,665	3,429	3,321
Nonoperating Income (Expense)									306	235	264
Revenues									3,971	3,664	3,585
Provision for Loan Losses Expensed									924	696	542
Noninterest Expense									1,667	1,633	1,614
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									1,380	1,335	1,429
Assets	116,347				115,636				116,347	115,636	113,188
Insurance Operations Member
Segment Reporting Information [Line Items]
Net Financing Revenue									61	57	56
Nonoperating Income (Expense)									1,036	1,033	1,129
Revenues									1,097	1,090	1,185
Provision for Loan Losses Expensed									0	0	0
Noninterest Expense									940	879	988
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									157	211	197
Assets	7,172				7,053				7,172	7,053	7,190
Mortgage Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue									97	57	36
Nonoperating Income (Expense)									0	0	0
Revenues									97	57	36
Provision for Loan Losses Expensed									(4)	7	3
Noninterest Expense									67	39	21
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									34	11	12
Assets	8,307				6,461				8,307	6,461	3,542
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue									121	89	59
Nonoperating Income (Expense)									26	25	32
Revenues									147	114	91
Provision for Loan Losses Expensed									10	9	(16)
Noninterest Expense									66	55	43
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									71	50	64
Assets	3,183				2,677				3,183	2,677	1,870
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue									(37)	87	(97)
Nonoperating Income (Expense)									162	(151)	(149)
Revenues									125	(64)	(246)
Provision for Loan Losses Expensed									(13)	(5)	(72)
Noninterest Expense									199	155	282
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest									(61)	(214)	(456)
Assets	$ 28,719				$ 26,754				$ 28,719	$ 26,754	$ 25,841