Other Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Other Liabilities
Interest rate swap contracts, Current	$ 7,314	$ 16,533
Asset retirement obligations	9,837	9,821
Deferred revenue, Current	3,590	249
Other, Current	10,629	1,634
Total current portion of other long-term liabilities	31,370	28,237
Acquisition-related contingent consideration	42,614
Interest rate swap contracts, Noncurrent	3,547	14,456
Deferred revenue, Noncurrent	2,063	1,698
Other, Noncurrent	26,778	2,537
Total other long-term liabilities	$ 75,002	$ 18,691