Other Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 BuyEfficient, LLC Y	Jan. 31, 2011 BuyEfficient, LLC
Other assets, net
Property and equipment, net	$ 2,318	$ 1,758
Intangible assets	8,476
Notes receivable	394	3,950
Other receivables	4,950	4,403
Other	3,439	2,632
Total other assets, net	19,577	12,743
Intangible assets
Percentage of equity interest purchased (as a percent)					50.00%
Intangible assets, net	149,242	32,656
Remaining useful life of intangibles, low end of range (in years)				7
Remaining useful life of intangibles, high end of range (in years)				20
Accumulated amortization	15,719	1,425		600
Amortization expense	$ 14,294	$ 281	$ 292	$ 600