Income Taxes - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Loss Carryforwards [Line Items]
Valuation allowance	$ 12,337	$ 17,940	$ 12,337
Statutory rate		21.00%	35.00%	35.00%
Provisional net income tax benefit due to Tax Cuts and Jobs Act	51,600
Provisional income tax benefit due to remeasurement of deferred taxes	59,700
Provisional income tax expense due to transition tax on foreign earnings	8,100
Decrease in deferred tax assets due to deemed mandatory repatriation	8,100
Undistributed earnings of foreign subsidiaries		$ 93,200
Unrecognized tax benefits	$ 318	306	$ 318	$ 343	$ 0
Income tax refunds				$ 28,400
U.S.
Operating Loss Carryforwards [Line Items]
Net operating loss carryforward		165,600
Net operating loss carryforwards subject to expiration		112,300
Valuation allowance		3,000
Foreign
Operating Loss Carryforwards [Line Items]
Valuation allowance		$ 15,000