Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Dec. 31, 2017
Financial Liabilities:
Contingent consideration		$ 6,200
Derivatives:
Increase in contingent consideration value	$ (1,100)
Interest Rate Swap
Derivatives:
Asset for Swaps		12,000
Recurring
Financial Assets:
Cash and cash equivalents	85,031	118,804
Restricted cash	10,826	11,065
Total	95,857	129,869
Financial Liabilities:
Contingent consideration	5,380	6,500
Total debt	1,831,004	1,780,547
Total	1,836,384	1,787,047
Recurring | Interest Rate Swap
Derivatives:
Asset for Swaps	22,961	11,985
Recurring | Level 1
Financial Assets:
Cash and cash equivalents	85,031	118,804
Restricted cash	2,268	0
Total	87,299	118,804
Financial Liabilities:
Contingent consideration	0	0
Total debt	0	0
Total	0	0
Recurring | Level 1 | Interest Rate Swap
Derivatives:
Asset for Swaps	0	0
Recurring | Level 2
Financial Assets:
Cash and cash equivalents	0	0
Restricted cash	8,558	11,065
Total	8,558	11,065
Financial Liabilities:
Contingent consideration	0	0
Total debt	1,831,004	1,780,547
Total	1,831,004	1,780,547
Recurring | Level 2 | Interest Rate Swap
Derivatives:
Asset for Swaps	22,961	11,985
Recurring | Level 3
Financial Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Total	0	0
Financial Liabilities:
Contingent consideration	5,380	6,500
Total debt	0	0
Total	5,380	6,500
Recurring | Level 3 | Interest Rate Swap
Derivatives:
Asset for Swaps	$ 0	$ 0