Revenue Recognition - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Jan. 01, 2018	Dec. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings	$ (72,360)			$ (71,453)
Deferred revenue	900
Deferred expense	600		$ 400
Operating expenses	(44,381)	$ (44,167)
Difference between Revenue Guidance in Effect before and after Topic 606 | Accounting Standards Update 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease to retained earnings			300
Deferred revenue			$ 700
Operating expenses	$ (3,546)