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Basis of Presentation and Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018
Revenue from External Customer [Line Items]
Revenue	$ 17,991		$ 14,718
Additions to tax positions of prior years		$ 547
Income tax penalties and interest accrued		55
Bill and Hold Arrangement
Revenue from External Customer [Line Items]
Revenue	$ 2,700
Minimum
Revenue from External Customer [Line Items]
Amortization period of capitalized contract costs	1 year
Tax Year 2017
Revenue from External Customer [Line Items]
Additions to tax positions of prior years		168
Tax Year 2016
Revenue from External Customer [Line Items]
Additions to tax positions of prior years		149
Tax Year 2015
Revenue from External Customer [Line Items]
Additions to tax positions of prior years		$ 230

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