Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jan. 01, 2019	Jan. 01, 2018
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 0	$ 0
Capitalized costs	0	0	$ 0
Advertising costs	1,800,000	1,700,000	2,100,000
Foreign currency gains (losses)	$ (3,100,000)	$ 1,100,000	$ (1,300,000)
Accounting Standards Update 2016-16
Summary Of Significant Accounting Policies [Line Items]
Reduction to other long-term assets resulting from cumulative effect					$ 7,700,000
Scenario, Forecast | Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Operating lease, right-of-use asset				$ 85,000,000
Operating lease liability				$ 86,000,000