Commitments and Contingencies - (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Obligations
Accrued liabilities for other litigation, claims, other disputes and governmental proceedings	$ 1,200	$ 1,300
Purchase obligations, total	34,600
Deferred tax liabilities	107,080	107,120
Tax Year 2022 To 2024
Obligations
Deferred tax liabilities	33,700
Tax Year 2029
Obligations
Deferred tax liabilities	37,800
Maximum
Obligations
Amount of letters of credit outstanding		100
Surety bonds
Obligations
Commitment obligations	$ 9,400	$ 8,600