Intangible Assets (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Intangible assets
Amortization expense of intangible assets	$ 1,794	$ 1,746	$ 1,746
Estimated future amortization expense for intangible assets
2013 (remaining nine months)	4,632
2014	7,316
2015	7,046
2016	6,126
2017	5,769
Thereafter	20,095
Total	50,984		51,978
Tradename
Estimated future amortization expense for intangible assets
Total	22,828		23,586
Tradename | Minimum
Intangible assets
Amortization Period	3 years
Tradename | Maximum
Intangible assets
Amortization Period	10 years
Non-compete agreements
Estimated future amortization expense for intangible assets
Total	4,023		4,130
Non-compete agreements | Minimum
Intangible assets
Amortization Period	2 years
Non-compete agreements | Maximum
Intangible assets
Amortization Period	5 years
Customer relationship
Estimated future amortization expense for intangible assets
Total	24,133		24,212
Customer relationship | Minimum
Intangible assets
Amortization Period	5 years
Customer relationship | Maximum
Intangible assets
Amortization Period	15 years
Backlog
Intangible assets
Amortization Period	9 months
Estimated future amortization expense for intangible assets
Total			$ 50