Convertible Senior Notes and Notes Payable (Details) (USD $)	3 Months Ended		9 Months Ended				9 Months Ended				9 Months Ended														9 Months Ended	1 Months Ended	3 Months Ended	9 Months Ended						9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Oct. 31, 2012	Dec. 31, 2011	Sep. 30, 2012 Amortizing debt facility secured by ACC Auto Finance segment [Member]		Dec. 31, 2011 Amortizing debt facility secured by ACC Auto Finance segment [Member]		Sep. 30, 2012 Amortizing debt facility secured by Auto Finance segment [Member]	Dec. 31, 2011 Amortizing debt facility secured by Auto Finance segment [Member]	Jan. 31, 2011 Amortizing debt facility secured by Auto Finance segment [Member]	Sep. 30, 2012 Software and equipment purchases secured by equipment [Member]	Dec. 31, 2011 Software and equipment purchases secured by equipment [Member]	Sep. 30, 2012 Investment secured by segment asset [Member]	Dec. 31, 2011 Investment secured by segment asset [Member]	Sep. 30, 2012 Expiring June 2013 [Member]	Dec. 31, 2011 Expiring June 2013 [Member]	Sep. 30, 2012 Expiring April 2014 [Member]	Dec. 31, 2011 Expiring April 2014 [Member]	Sep. 30, 2012 Expiring January 2015 [Member]	Dec. 31, 2011 Expiring January 2015 [Member]	Sep. 30, 2012 CAR [Member]	Sep. 30, 2012 Interest rate swap [Member]	May 31, 2005 3.625% convertible senior notes due 2025 [Member]	Sep. 30, 2011 3.625% convertible senior notes due 2025 [Member]	Sep. 30, 2011 3.625% convertible senior notes due 2025 [Member]	Sep. 30, 2012 3.625% convertible senior notes due 2025 [Member]	Dec. 31, 2011 3.625% convertible senior notes due 2025 [Member]	Sep. 30, 2012 5.875% convertible senior notes due 2035 [Member]	Dec. 31, 2011 5.875% convertible senior notes due 2035 [Member]	May 31, 2005 5.875% convertible senior notes due 2035 [Member]	Sep. 30, 2012 Senior notes [Member]
Debt Instrument [Line Items]
Aggregate principal amount																		$ 217,700,000		$ 91,200,000		$ 1,200,000				$ 250,000,000			$ 450,000	$ 83,943,000	$ 139,467,000	$ 139,467,000	$ 300,000,000
Interest rate on notes (in hundredths)																													3.625%		5.875%
Repurchased face amount of notes																										83,500,000	6,000,000	39,600,000
Components of consolidated balance sheets associated with our convertible senior notes [Abstract]
Face amount																		217,700,000		91,200,000		1,200,000				250,000,000			450,000	83,943,000	139,467,000	139,467,000	300,000,000
Discount	(44,723,000)		(44,723,000)			(47,010,000)
Net carrying value	95,194,000		95,194,000			176,400,000
Carrying amount of equity component included in additional paid-in capital	108,714,000		108,714,000			108,714,000
Excess of instruments' if-converted values over face principal amounts	0		0			0
Amortization associated with discount to face amount of notes	200,000	1,500,000	2,287,000	5,112,000
Interest expense incurred during the period	2,000,000	3,100,000	7,400,000	9,600,000
Weighted average effective interest rate (in hundredths)																																		9.20%
Repurchase amount of notes																											5,700,000	37,000,000
Gain on repurchase of convertible senior notes	0	138,000	0	607,000
Notes Payable Associated with Structured Financings, at Fair Value [Abstract]
Total structured financing notes reported at fair value that are secured by credit card receivables and to which we are subordinated	167,521,000		167,521,000			241,755,000												110,400,000	154,100,000	56,000,000	81,600,000	1,100,000	6,100,000
Weighted average interest rate (in hundredths)																		3.30%		4.90%		2.00%
Credit card receivables and restricted cash, carrying amount, as security for notes payable	175,800,000		175,800,000															110,400,000		59,800,000		5,600,000
Maximum aggregate exposure to pre-tax equity loss associated with structured financing at fair value	8,300,000		8,300,000
Notes Payable Associated with Structured Financings, at Face Value [Abstract]
Total asset-backed structured financing notes outstanding	7,366,000		7,366,000			23,151,000	7,200,000	[1]	20,400,000	[1]	0	2,600,000	9,400,000	200,000	0	0	200,000
Minimum fixed rate of debt facility (in hundredths)							15.00%
Carrying amount of receivables as security for structured financing notes							12,600,000				800,000
Implied rate of interest														15.00%
Percentage of receivables allocated as compensation after repayment of notes (in hundredths)							37.50%
Liability for accrued interest							3,700,000		1,500,000
Amount of notes received on sale of segment operation											2,400,000
Effective interest rate on loan (in hundredths)							25.80%																		4.75%
Maximum aggregate exposure to pre-tax equity loss associated with structured financing at face value	5,200,000		5,200,000
Notes Payable, at Face Value [Abstract]
Credit facility maximum amount	40,000,000		40,000,000		20,000,000											200,000
Outstanding eligible principal receivables	20,184,000		20,184,000			23,765,000										184,000								20,000,000	20,000,000
Carrying value of financial and operating assets	$ 406,612,000	$ 710,838,000	$ 406,612,000	$ 710,838,000		$ 647,907,000																		$ 50,100,000
Variable rate basis of new facility			LIBOR + 4.0%
Interest rate (in hundredths)	4.75%		4.75%		6.00%
Description of variable rate basis																									LIBOR
Basis spread of interest rate (in hundredths)																									4.00%

[1] The terms of this lending agreement provide for the application of all excess cash flows from the underlying auto finance receivables portfolio (above and beyond interest costs and contractual servicing compensation to our outsourced third-party servicer) to reduce outstanding debt balances. The terms of this facility provide that 37.5% of any cash flows (net of contractual servicing compensation) generated on the auto finance receivables portfolio after repayment of the notes will be allocated to the note holders as additional compensation for the use of their capital. Based on current estimates of this additional compensation, we currently are accruing interest expense on this loan at a 25.8% effective interest rate, and our liability for such accrued interest grew from $1.5 million as of December 31, 2011 to $3.7 million as of September 30, 2012, which is included as a component of the debt facility balance listed above.