Income Taxes Tax Reform (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent		35.00%	35.00%	35.00%
Effective Income Tax Rate Reconciliation, Future Federal Statutory Income Tax Rate, Percent		21.00%
Income Tax Reconciliation, Tax Reform		$ 12,660	$ 0	$ 0
Undistributed Earnings of Foreign Subsidiaries	$ 110,000	$ 110,000
Deferred Tax Asset Revaluation [Member]
Income Tax Reconciliation, Tax Reform	3,700
Repatriation of Undistributed Non-U.S. Subsidiary Earnings [Member]
Income Tax Reconciliation, Tax Reform	$ 9,000