Leases - Lease-related Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Operating leases:
Other assets	$ 24,471
Other current liabilities	4,247
Other liabilities	22,836
Total operating lease liabilities	27,083
Finance leases:
Property and equipment, net	68,810
Finance lease obligations—current	9,927	$ 3,884
Finance lease obligations—net of current portion	59,610	$ 2,095
Total finance lease liabilities	$ 69,537