Income Taxes Provision for income taxes (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 12,617	$ 20,004	$ 7,556
Current Federal Tax Expense (Benefit)	492	2,774	21,123
Current State and Local Tax Expense (Benefit)	1,865	2,263	2,347
Current Foreign Tax Expense (Benefit)	9,136	3,170	1,118
Current Income Tax Expense (Benefit)	11,493	8,207	24,588
Deferred Federal Income Tax Expense (Benefit)	(9,118)	(20,878)	(2,045)
Deferred State and Local Income Tax Expense (Benefit)	(3,072)	(4,619)	(767)
Deferred Foreign Income Tax Expense (Benefit)	(5,722)	(71)	304
Deferred Income Tax Expense (Benefit)	(17,912)	(25,568)	(2,508)
PROVISION FOR INCOME TAXES	$ (6,419)	$ (17,361)	$ 22,080