Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Cash flow hedge Interest rate swaps	Mar. 31, 2013 Cash flow hedge Interest rate swaps	Mar. 31, 2014 Level 3 Contingent acquisition consideration	Mar. 31, 2014 Level 3 Contingent acquisition consideration Minimum	Mar. 31, 2014 Level 3 Contingent acquisition consideration Maximum	Mar. 31, 2014 Recurring basis Level 2 Prepaid expenses and other	Dec. 31, 2013 Recurring basis Level 2 Prepaid expenses and other	Mar. 31, 2014 Recurring basis Level 3 Contingent acquisition consideration Accrued expenses	Dec. 31, 2013 Recurring basis Level 3 Contingent acquisition consideration Accrued expenses	Mar. 31, 2014 Recurring basis Level 3 Contingent acquisition consideration Other long term liabilities	Dec. 31, 2013 Recurring basis Level 3 Contingent acquisition consideration Other long term liabilities
Assets:
Interest Rate Swaps						$ 804	$ 824
Liabilities:
Contingent acquisition consideration								1,366	1,374	195	163
Fair Value Inputs
Probability of contingent consideration (as a percent)				5.00%	100.00%
Weighted average discount rate (as a percent)			11.00%
Ineffective portion of cash flow hedges recognized	$ 0	$ 0