Acquisitions - AQSense, S.L. Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Aug. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 95,280		$ 81,448	$ 77,388
AQSense, S.L. [Member]
Business Acquisition [Line Items]
Accounts receivable		$ 168
Goodwill		1,383
Accrued expenses		(14)
Purchase price		2,519
Customer Relationships [Member] | AQSense, S.L. [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets		598
Technology-Based Intangible Assets [Member] | AQSense, S.L. [Member]
Business Acquisition [Line Items]
Finite-lived intangible assets		$ 384