Subsequent Events (Details) (USD $)	3 Months Ended			9 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Dec. 31, 2010
Subsequent Event [Line Items]
Net revenue		$ 95,793,000	$ 63,128,000	$ 262,035,000	$ 181,820,000
Percentage of equity interest		19.90%		19.90%
Property and equipment		20,780,000		20,780,000		18,875,000
Goodwill		233,428,000		233,428,000		136,408,000
Intangible assets		100,978,000		100,978,000		23,163,000
Professional fees associated with acquisition	1,600,000	800,000		900,000
ALG [Member]
Subsequent Event [Line Items]
Net revenue		2,700,000	2,000,000	7,600,000	6,200,000
Carrying value of net assets		46,100,000		46,100,000
Property and equipment		1,800,000		1,800,000
Goodwill		33,100,000		33,100,000
Intangible assets		2,500,000		2,500,000
Other net assets		1,200,000		1,200,000
TrueCar [Member]
Subsequent Event [Line Items]
Percentage of equity interest		15.00%		15.00%
Estimated carrying value of the investment		88,000,000		88,000,000
Fair value of the shares received		82,500,000		82,500,000
Additional cash investment		7,500,000		7,500,000
Fair value of warrant received		5,500,000		5,500,000
Term of the warrant (in years)		1		1
Measurement period of additional payment		3		3
Gross cash proceeds		125,000,000		125,000,000
Fair value of data license		5,600,000		5,600,000
Maximum payment		7,000,000		7,000,000
Estimated useful life (in years)				5
Expect to recognize a pre-tax gain on sale		47,500,000		47,500,000
Expect to recognize a gain on sale, net of tax		28,800,000		28,800,000
Consideration received on sale		$ 93,600,000		$ 93,600,000