Leases - Lease Assets and Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Operating leases:
Operating lease right-of-use assets	$ 57,269	$ 0
Accrued liabilities	16,144	0
Operating lease liabilities	59,140	$ 0
Total operating lease liabilities	$ 75,284