Summary of Significant Accounting Policies (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jan. 01, 2019
Summary Of Significant Accounting Policies [Line Items]
Restricted cash	$ 0	$ 0	$ 0
Capitalized costs	0	0	0
Advertising costs	1,500,000	1,800,000	1,700,000
Foreign currency gains (losses)	(1,100,000)	(3,100,000)	$ 1,100,000
Operating lease liability	82,753,000
Operating lease right-of-use asset	80,607,000	0		$ 83,707,000
Other current assets	124,982,000	108,220,000		107,228,000
Straight-line lease liabilities	81,164,000	$ 84,826,000
Stranded tax effects				1,700,000
Accounting Standards Update 2016-02
Summary Of Significant Accounting Policies [Line Items]
Operating lease liability				86,700,000
Operating lease right-of-use asset				83,707,000
Other current assets	1,000,000.0			$ (992,000)
Straight-line lease liabilities	$ 4,000,000.0