Segment Information (Financial Information Operating Segments) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Segment Reporting Information [Line Items]
Net Financing Revenue	$ 979	$ 951
Nonoperating Income (Expense)	396	376
Revenues	1,375	1,327
Provision for Loan Losses Expensed	271	220
Noninterest Expense	778	710
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	326	397
Assets	162,101	156,505	$ 163,728
Net Interest Income (Loss) after Provision for Loan Losses	708	731
Automotive Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	892	896
Nonoperating Income (Expense)	101	77
Revenues	993	973
Provision for Loan Losses Expensed	268	209
Noninterest Expense	437	427
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	288	337
Assets	115,154	112,289
Insurance Operations Member
Segment Reporting Information [Line Items]
Net Financing Revenue	15	14
Nonoperating Income (Expense)	264	254
Revenues	279	268
Provision for Loan Losses Expensed	0	0
Noninterest Expense	239	218
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	40	50
Assets	7,230	7,194
Mortgage Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	34	20
Nonoperating Income (Expense)	0	0
Revenues	34	20
Provision for Loan Losses Expensed	1	3
Noninterest Expense	24	15
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	9	2
Assets	8,362	7,493
Corporate Finance Operations [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	34	28
Nonoperating Income (Expense)	18	6
Revenues	52	34
Provision for Loan Losses Expensed	6	6
Noninterest Expense	21	17
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	25	11
Assets	3,438	2,839
Corporate and Other [Member]
Segment Reporting Information [Line Items]
Net Financing Revenue	4	(7)
Nonoperating Income (Expense)	13	39
Revenues	17	32
Provision for Loan Losses Expensed	(4)	2
Noninterest Expense	57	33
Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest	(36)	(3)
Assets	$ 27,917	$ 26,690