Income Taxes - Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
U.S. federal statutory income tax rate and effective tax rate
U.S. federal statutory income tax rate (as a percent)	35.00%	21.00%	35.00%	35.00%
State and local income taxes, net of U.S. federal income tax effect (as a percent)		(0.64%)	0.60%	5.20%
Foreign tax impact, net (as a percent)		(32.40%)	(81.80%)	6.20%
Valuation allowance		86.10%	585.80%
Tax impact of Tax Cuts and Jobs Act			149.20%
Stock windfall/shortfall		(3.80%)	(13.50%)
Reserves released upon tax settlement		(16.80%)		18.60%
Non-deductible costs (as a percent)		43.00%	21.30%	(22.80%)
Other, net (as a percent)		(3.30%)	7.90%	(2.10%)
Effective income tax rate (as a percent)		93.20%	704.50%	40.10%
Reconciliation of the beginning and ending amounts of unrecognized tax benefits
Balance, January 1		$ 7,693	$ 7,356	$ 15,553
Additions based on tax positions related to the current year		322	591	66
Additions based on tax positions of prior years		38	4	406
Reductions for tax positions of prior years			(13)
Reductions due to settlements with taxing authorities		(987)	(64)	(2,153)
Reductions due to expiration of statute of limitations		(1,209)	(181)	(6,516)
Balance, December 31	$ 7,693	5,857	7,693	7,356
Amount of unrecognized tax benefits that was netted against fully reserved U.S. deferred tax assets	$ 4,500	4,600	4,500
Accrued interest expense related to tax reserves, net of related tax effects		1,700
Net (reductions) additions of unrecognized tax-related interest expense		(400)	(100)	2,500
Penalties recognized, as a component of income tax expense		$ 0	$ 100	$ 0