Fair Value of Financial Instruments Financial Instruments Carried at Historical Costs (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	$ 2,317,335	$ 2,256,312
Revolving credit facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	300,912	225,155
Other debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	13,492	2,419
Credit agreement [Member] | United States term loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	1,190,683	1,204,714
Credit agreement [Member] | U.K. term loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	127,826	124,747
Australian Credit Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	501,385	513,192
Australian Partner Loan Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Carrying Value	183,037	186,085
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	2,338,840	2,279,901
Fair Value, Inputs, Level 2 [Member] | Revolving credit facility [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	304,495	229,483
Fair Value, Inputs, Level 2 [Member] | Other debt [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	13,522	2,426
Fair Value, Inputs, Level 2 [Member] | Credit agreement [Member] | United States term loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	1,193,427	1,208,657
Fair Value, Inputs, Level 2 [Member] | Credit agreement [Member] | U.K. term loan [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	129,372	126,480
Fair Value, Inputs, Level 2 [Member] | Australian Credit Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	514,325	528,105
Fair Value, Inputs, Level 2 [Member] | Australian Partner Loan Agreement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term Debt, Fair Value	$ 183,699	$ 184,750