Description of Business and Significant Accounting Policies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jan. 01, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment of adopting ASU 2016-09				$ 97
Allowance for Doubtful Accounts Receivable [Roll Forward]
Beginning balance	$ 1,091	$ 1,856	$ 1,947
Additions	1,720	368	17
Deductions	(319)	(1,133)	(108)
Ending balance	$ 2,492	$ 1,091	$ 1,856
Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment of adopting ASU 2016-09				(137)
Accounting Standards Update 2016-09 | Retained Earnings
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect adjustment of adopting ASU 2016-09				$ 100