Other Assets and Accrued Liabilities - Long-Term Assets (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Derivatives, Fair Value [Line Items]
Deferred contract and other costs	$ 20,242		$ 2,914
Deferred charges and other assets, net	33,934	$ 29,797	13,690
Deferred charges and other assets, net | Interest rate swap
Derivatives, Fair Value [Line Items]
Interest rate swaps	$ 13,692		$ 10,776