Description of Business and Summary of Significant Accounting Policies (Advertising and Sales Commission) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Capitalized Direct Response Advertising Costs [Line Items]
Deferred revenue included in accounts receivables	$ 10,200	$ 5,200
Advertising Expense	7,500	6,100	$ 6,200
Capital Direct Response Advertising, Amortization		3,900
Capitalized Direct Response Advertising Costs, net		1,900
Deferred Sales Commission	661	574
Amortization of Deferred Sales Commissions	$ 1,000	$ 1,100
Minimum
Capitalized Direct Response Advertising Costs [Line Items]
Capitalized Direct Response Advertising Costs, Amortization Period	12 months
Maximum
Capitalized Direct Response Advertising Costs [Line Items]
Capitalized Direct Response Advertising Costs, Amortization Period	24 months
ASC 340-40
Capitalized Direct Response Advertising Costs [Line Items]
New Accounting Pronouncement Or Change In Account Principle, Effect Of Amortization Period Adjustment To Production Costs	$ 1,900
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Net Income	$ 522