Guarantor Consolidating Financial Statements Current Period Guarantor Balance Sheet (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2010
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,074	$ 1,074	$ 1,289	$ 1,289	$ 572	$ 194
Finance receivables, net	29,282		10,998
Restricted cash	1,958		744
Property and equipment, net	132		52
Leased vehicles, net	3,383		1,703
Deferred Tax Assets, Net	359		107
Goodwill	1,240		1,108
Due from Related Parties	129		66
Other assets	433		130
Due from Affiliates	0
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Assets	37,990		16,197
Secured debt	22,073		9,378
Unsecured debt	6,973		1,500
Accounts payable and accrued expenses	946		217
Deferred income	168		70
Deferred income taxes	87
Taxes payable	287		93
Related party taxes payable	643		559
Derivative Liability	160		1
Due to Affiliate	0
Liabilities	31,705		11,818
Common stock, $0.01 par value per share, 1,000 shares authorized and 502 issued	0
Additional Paid in Capital, Common Stock	4,785		3,459
Accumulated Other Comprehensive Income (Loss), Net of Tax	11		(3)		(7)
Retained Earnings (Accumulated Deficit)	1,489		923
Total stockholders' equity	6,285		4,379
Total liabilities and shareholder's equity	37,990		16,197
Parent Company [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Deferred Tax Assets, Net	1		39
Goodwill	1,095		1,095
Due from Related Parties	29		66
Other assets	74		14
Due from Affiliates	3,754		2,063
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	6,994		3,274
Assets	11,947		6,551
Unsecured debt	4,000		1,500
Accounts payable and accrued expenses	101		22
Deferred income	0
Deferred income taxes	(28)
Taxes payable	83		91
Related party taxes payable	643		559
Derivative Liability	0
Due to Affiliate	863
Liabilities	5,662		2,172
Additional Paid in Capital, Common Stock	4,785		3,459
Accumulated Other Comprehensive Income (Loss), Net of Tax	11		(3)
Retained Earnings (Accumulated Deficit)	1,489		923
Total stockholders' equity	6,285		4,379
Total liabilities and shareholder's equity	11,947		6,551
Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	395	395	1,252	1,252	501	185
Finance receivables, net	612		1,558
Restricted cash	20
Property and equipment, net	5		4
Leased vehicles, net	0
Deferred Tax Assets, Net	0		(28)
Goodwill	0
Due from Related Parties	0
Other assets	5		18
Due from Affiliates	863
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	3,565		2,193
Assets	5,465		4,997
Accounts payable and accrued expenses	133		90
Deferred income taxes	161
Taxes payable			4
Derivative Liability	14
Due to Affiliate	1,474		1,669
Liabilities	1,782		1,763
Additional Paid in Capital, Common Stock	79		79
Accumulated Other Comprehensive Income (Loss), Net of Tax	(8)		(11)
Retained Earnings (Accumulated Deficit)	3,612		3,166
Total stockholders' equity	3,683		3,234
Total liabilities and shareholder's equity	5,465		4,997
Non-Guarantor Subsidiaries [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Cash and cash equivalents	679	679	37	37	71	9
Finance receivables, net	28,670		9,440
Restricted cash	1,938		744
Property and equipment, net	127		48
Leased vehicles, net	3,383		1,703
Deferred Tax Assets, Net	358		96
Goodwill	145		13
Due from Related Parties	100
Other assets	358		98
Due from Affiliates
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	0
Assets	35,758		12,179
Secured debt	22,073		9,378
Unsecured debt	2,973
Accounts payable and accrued expenses	716		105
Deferred income	168		70
Deferred income taxes	(46)
Taxes payable	204		(2)
Related party taxes payable	1
Derivative Liability	146		1
Due to Affiliate	2,280		394
Liabilities	28,883		9,946
Common stock, $0.01 par value per share, 1,000 shares authorized and 502 issued	532		570
Additional Paid in Capital, Common Stock	3,833		123
Accumulated Other Comprehensive Income (Loss), Net of Tax	24		13
Retained Earnings (Accumulated Deficit)	2,486		1,527
Total stockholders' equity	6,875		2,233
Total liabilities and shareholder's equity	35,758		12,179
Consolidation, Eliminations [Member]
Condensed Balance Sheet Statements, Captions [Line Items]
Deferred Tax Assets, Net	0
Due from Related Parties
Other assets	(4)
Due from Affiliates	(4,617)		(2,063)
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures	(10,559)		(5,467)
Assets	(15,180)		(7,530)
Accounts payable and accrued expenses	(4)
Related party taxes payable	(1)
Due to Affiliate	(4,617)		(2,063)
Liabilities	(4,622)		(2,063)
Common stock, $0.01 par value per share, 1,000 shares authorized and 502 issued	(532)		(570)
Additional Paid in Capital, Common Stock	(3,912)		(202)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(16)		(2)
Retained Earnings (Accumulated Deficit)	(6,098)		(4,693)
Total stockholders' equity	(10,558)		(5,467)
Total liabilities and shareholder's equity	$ (15,180)		$ (7,530)