Fair Value of Financial Instruments Financial Instruments Carried at Historical Cost(Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,256,312	$ 2,273,058
Long-term debt, Fair Value	2,279,901	2,303,531
Revolving credit facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	225,155	74,297
Long-term debt, Fair Value	229,483	81,192
Other debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,419	4,882
Long-term debt, Fair Value	2,426	4,889
Credit Agreement [Member] | United States Term Loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	1,204,714	1,415,873
Long-term debt, Fair Value	1,208,657	1,422,512
Credit Agreement [Member] | U.K. term loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	124,747	121,149
Long-term debt, Fair Value	126,480	121,594
Australia Credit Agreement
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	513,192	484,703
Long-term debt, Fair Value	528,105	501,909
Partner Loan Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	186,085	172,154
Long-term debt, Fair Value	$ 184,750	$ 171,435