New Accounting Pronouncements New Accounting Pronouncements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Sales Commissions and Fees	$ 8,200
Net Cash Provided by (Used in) Operating Activities	65,566	$ 39,881	$ 50,917
Income Tax Expense (Benefit)	(26,755)	4,711	14,646
Net Cash Provided by (Used in) Financing Activities	(34,881)	182,543	(12,622)
Accounting Standards Update 2016-09, Statutory Tax Withholding Component [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by (Used in) Operating Activities		1,700	2,800
Income Tax Expense (Benefit)	$ (600)
Net Cash Provided by (Used in) Financing Activities		$ (1,700)	$ (2,800)