Income Taxes Income Tax Expense Reconciliation (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Expense (Benefit), Continuing Operations, Income Tax Reconciliation
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	35.00%	35.00%	35.00%
Income Tax Reconciliation, Income Tax Expense (Benefit), at Federal Statutory Income Tax Rate	$ 23,170	$ (20,380)	$ (7,740)
Income Tax Reconciliation, State and Local Income Taxes	2,250	(550)	(520)
Income Tax Reconciliation, Foreign Income Tax Rate Differential	(2,580)	(1,930)	110
Income Tax Reconciliation, Tax Contingencies	(480)	(1,410)	(460)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Impairment Losses, Amount	0	5,050	11,430
Effective Income Tax Rate Reconciliation, Tax Exempt Income, Amount	(1,050)	(310)	(980)
Effective Income Tax Rate Reconciliation, Tax Credit, Research, Amount	(1,510)	(830)	(1,680)
Income Tax Reconciliation, Tax on Undistributed Foreign Earnings	(430)	340	610
Income Tax Reconciliation, Change in Deferred Tax Assets Valuation Allowance	520	2,140	3,770
Income Tax Reconciliation, Tax Reform	12,660	0	0
Income Tax Reconciliation, Other Adjustments	2,700	(550)	2,000
Income Tax Expense (Benefit), Continuing Operations	$ 35,250	$ (18,430)	$ 6,540