Fair Value Measurements (Details 2) (USD $) In Thousands, unless otherwise specified	9 Months Ended		0 Months Ended	3 Months Ended	9 Months Ended	0 Months Ended	9 Months Ended			0 Months Ended	9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Mar. 11, 2013 FSSI acquisition	Jun. 30, 2013 FSSI acquisition	Sep. 30, 2013 FSSI acquisition	Mar. 12, 2012 Sprint sellers	Sep. 30, 2012 Sprint sellers	Sep. 30, 2012 Saxon Group	Sep. 30, 2013 Contingent consideration item	Mar. 11, 2013 Contingent consideration FSSI acquisition	Sep. 30, 2013 Contingent consideration Rockford sellers	Sep. 30, 2013 Contingent consideration Sprint sellers
Rollforward of contingent consideration liability level three fair value measurements
Balance at the beginning of the period									$ 23,431
Additions										702
Change in fair value of contingent consideration	(9,287)	(2,489)							1,613
Payments	(2,273)	(38,110)	(1,025)	(650)	(1,675)	(21,197)	(21,197)	(2,979)			(6,900)	(4,000)
Balance at the end of the period									$ 14,846
Additional information
Number of unobservable inputs									2
Minimum probability of acquired entity meeting contractual operating performance target (as a percent)									33.00%
Maximum probability of acquired entity meeting contractual operating performance target (as a percent)									100.00%