Income Taxes Operating Loss Carryforwards (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating loss carryforwards [Abstract]
Employee Service Share-based Compensation, Tax Benefit from Exercise of Stock Options	$ 20,004	$ 7,556	$ 9,330
UNITED STATES
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	4,900
Foreign Tax Authority [Member]
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	6,600
OperatingLossCarryforwardNet	1,100
Operating Loss Carryforwards, Valuation Allowance	$ 5,500