Segment and Geographic Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 996	$ 970	$ 2,931	$ 2,736
Nonoperating Income (Expense)	388	332	1,138	786
Revenues	1,384	1,302	4,069	3,522
Provision for Loan Losses Expensed	258	211	650	467
Noninterest Expense	735	674	2,218	2,093
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	391	417	1,201	962
Assets	157,397	155,916	157,397	155,916	$ 158,581
Net Interest Income (Loss) after Provision for Loan Losses	738	759	2,281	2,269
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	933	870	2,758	2,529
Nonoperating Income (Expense)	74	63	228	170
Revenues	1,007	933	2,986	2,699
Provision for Loan Losses Expensed	270	201	649	460
Noninterest Expense	418	409	1,255	1,237
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	319	323	1,082	1,002
Assets	113,669	113,843	113,669	113,843
Insurance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	14	16	44	42
Nonoperating Income (Expense)	264	233	777	769
Revenues	278	249	821	811
Provision for Loan Losses Expensed	0	0	0	0
Noninterest Expense	222	209	733	678
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	56	40	88	133
Assets	7,259	6,997	7,259	6,997
Mortgage Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	25	17	71	39
Nonoperating Income (Expense)	0	0	0	0
Revenues	25	17	71	39
Provision for Loan Losses Expensed	1	3	4	9
Noninterest Expense	16	10	48	28
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	8	4	19	2
Assets	7,933	6,326	7,933	6,326
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	30	22	87	64
Nonoperating Income (Expense)	4	10	14	22
Revenues	34	32	101	86
Provision for Loan Losses Expensed	3	4	12	3
Noninterest Expense	16	14	49	42
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	15	14	40	41
Assets	3,232	2,269	3,232	2,269
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	(6)	45	(29)	62
Nonoperating Income (Expense)	46	26	119	(175)
Revenues	40	71	90	(113)
Provision for Loan Losses Expensed	(16)	3	(15)	(5)
Noninterest Expense	63	32	133	108
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(7)	36	(28)	(216)
Assets	$ 25,304	$ 26,481	$ 25,304	$ 26,481