Description of Business and Summary of Significant Accounting Policies (Deferred Revenue Rollforward) (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred Revenue, beginning of period	$ 38,030
Recognition of Deferred Revenue	(21,697)
Deferred Revenue acquired in acquisition	16,273
Deferred Revenue, Additions	12,054
Deferred Revenue, end of period	44,660
Calculated under Revenue Guidance in Effect before Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Deferred Revenue, beginning of period	23,985
Accounting Standards Update 2014-09 Adjustments | Difference between Revenue Guidance in Effect before and after Topic 606 [Member]
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Deferred Revenue	$ 14,045