Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating leases
Amount of damages awarded in binding arbitration against a former employee for violation of a non-competition agreement	$ 3,500,000
Period of operating leases	15 years
Lease obligations for office and storage facilities, including amounts of escalating operating lease rental payments
2013	10,600,000
2014	12,564,000
2015	12,744,000
2016	11,667,000
2017	9,068,000
Thereafter	65,996,000
Total	122,639,000
Rent expense, net of sublease rentals	14,900,000	9,200,000	6,200,000
Sublease rentals	$ 300,000	$ 200,000	$ 200,000
Minimum
Operating leases
Period of operating leases	3 years
Number of renewal options	1
Maximum
Operating leases
Period of operating leases	10 years