Other Assets and Accrued Liabilities - Long-Term Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Other Liabilities Disclosure [Abstract]
Non-current portion of deferred revenues	$ 12,541		$ 12,593
Noncurrent portion of financing leases	1,226
Other	1,267		1,771
Other liabilities	$ 15,034	$ 16,008	$ 14,364