Long-term Debt Debt Issuance Costs (Details) $ in Thousands, AUD in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2016 AUD	Dec. 31, 2016 USD ($)
Debt Issuance Costs, Gross	$ 43,950				$ 42,495
Accumulated Amortization, Debt Issuance Costs	(18,775)				(9,309)
Debt Issuance Costs, Net	$ 25,175				33,186
Debt Issuance Cost, Weighted Average Amortization Period	2 years 6 months	3 years
Amortization of Debt Issuance Costs	$ 9,300	$ 7,700	$ 7,600
2018	9,042
2019	8,959
2020	4,385
2021	2,789
2022	$ 0
Credit Agreement [Member]
Debt Issuance Costs, Gross			5,800		3,000
Write off of Deferred Debt Issuance Cost		$ 1,300	$ 2,000
Australia Credit Agreement
Debt Issuance Costs, Gross				AUD 19.8	$ 14,700