Debt - Amended Credit Agreement (Details)	Mar. 23, 2017 USD ($)	Mar. 31, 2018 AUD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Mar. 23, 2017 AUD ($)	Mar. 23, 2017 USD ($)	Mar. 22, 2017 AUD ($)	Mar. 22, 2017 USD ($)
Debt Instrument [Line Items]
Loan costs			$ 7,273,000	$ 7,612,000
Term loan			792,000,000	794,000,000
Revolver			$ 330,155,000	$ 270,559,000
Weighted average interest rate		4.20%	4.20%
Revolver
Debt Instrument [Line Items]
Revolver			$ 330,000,000
Additional Revolver
Debt Instrument [Line Items]
Borrowing capacity increase			500,000,000
Revolving Credit Facility | Line of Credit | Amended Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 900,000,000
Leverage ratio					2.50	2.50
Total leverage ratio, maximum					6.25	6.25
Senior secured leverage ratio					3.50	3.50
Interest coverage ratio					3.00	3.00
Revolving Credit Facility | Line of Credit | Amended Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate					2.25%	2.25%
Letter of Credit
Debt Instrument [Line Items]
Long-term debt			70,000,000
Letter of Credit | Line of Credit | Amended Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity					$ 275,000,000		$ 225,000,000
Loan costs						$ 7,000,000
Letter of Credit | Line of Credit | Bank Guarantee and Standby Sub Facility
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 100,000,000	77,000,000
Accordion | Line of Credit | Amended Credit Agreement
Debt Instrument [Line Items]
Accordion feature, increase limit	$ 450,000,000
Term Loan
Debt Instrument [Line Items]
Term loan			$ 792,000,000
Term Loan | Line of Credit | Amended Credit Agreement
Debt Instrument [Line Items]
Maximum borrowing capacity						$ 800,000,000		$ 291,000,000
Term Loan | Line of Credit | Amended Credit Agreement | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate					2.25%	2.25%
Interest rate					0.75%	0.75%