Fair Value Measurement (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended			6 Months Ended
	Jun. 30, 2014 Cash flow hedge Interest rate swaps	Jun. 30, 2013 Cash flow hedge Interest rate swaps	Jun. 30, 2014 Contingent acquisition consideration	Jun. 30, 2014 Level 3 Contingent acquisition consideration	Jun. 30, 2014 Level 3 Contingent acquisition consideration Minimum	Jun. 30, 2014 Level 3 Contingent acquisition consideration Maximum	Jun. 30, 2014 Recurring basis Level 2 Prepaid expenses and other	Dec. 31, 2013 Recurring basis Level 2 Prepaid expenses and other	Jun. 30, 2014 Recurring basis Level 3 Contingent acquisition consideration Accrued expenses	Dec. 31, 2013 Recurring basis Level 3 Contingent acquisition consideration Accrued expenses	Jun. 30, 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							$ 357	$ 824
Liabilities:
Contingent acquisition consideration			1,620						1,866	1,374	187	163
Fair Value Inputs
Probability of contingent consideration (as a percent)					10.00%	50.00%
Ineffective portion of cash flow hedges recognized	$ 0	$ 0
Weighted average discount rate (as a percent)				12.00%