Segment Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 1,067	$ 984	$ 2,046	$ 1,935
Nonoperating Income (Expense)	388	374	784	750
Revenues	1,455	1,358	2,830	2,685
Provision for Loan Losses Expensed	269	172	540	392
Noninterest Expense	810	773	1,588	1,483
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	376	413	702	810
Assets	164,345	157,931	164,345	157,931	$ 163,728
Net Interest Income (Loss) after Provision for Loan Losses	798	812	1,506	1,543
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	932	929	1,824	1,825
Nonoperating Income (Expense)	107	77	208	154
Revenues	1,039	1,006	2,032	1,979
Provision for Loan Losses Expensed	266	170	534	379
Noninterest Expense	426	410	863	837
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	347	426	635	763
Assets	115,447	112,356	115,447	112,356
Insurance Operations Member
Segment Reporting Information [Line Items]
Net Financing Revenue	14	16	29	30
Nonoperating Income (Expense)	245	259	509	513
Revenues	259	275	538	543
Provision for Loan Losses Expensed	0	0	0	0
Noninterest Expense	280	293	519	511
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(21)	(18)	19	32
Assets	7,308	7,193	7,308	7,193
Mortgage Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	32	26	66	46
Nonoperating Income (Expense)	1	0	1	0
Revenues	33	26	67	46
Provision for Loan Losses Expensed	1	0	2	3
Noninterest Expense	25	17	49	32
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	7	9	16	11
Assets	8,902	8,014	8,902	8,014
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	48	29	82	57
Nonoperating Income (Expense)	10	4	28	10
Revenues	58	33	110	67
Provision for Loan Losses Expensed	6	3	12	9
Noninterest Expense	17	16	38	33
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	35	14	60	25
Assets	3,552	2,989	3,552	2,989
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	41	(16)	45	(23)
Nonoperating Income (Expense)	25	34	38	73
Revenues	66	18	83	50
Provision for Loan Losses Expensed	(4)	(1)	(8)	1
Noninterest Expense	62	37	119	70
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	8	(18)	(28)	(21)
Assets	$ 29,136	$ 27,379	$ 29,136	$ 27,379