Deferred revenue	3 Months Ended
Deferred revenue	Mar. 31, 2018
Revenue Recognition [Abstract]
Deferred revenue	Deferred revenue Short-term deferred revenue of $95.7 million and $78.8 million includes deferred revenue from product sales and service contracts, net of deferred cost of sales of $15.7 million and $16.9 million as of March 31, 2018 and December 31, 2017, respectively. The short-term deferred revenues from product sales relate to delivered and invoiced products, pending installation and acceptance, expected to occur within the next twelve months. Long-term deferred revenue includes deferred revenue from service contracts of $8.8 million and $10.6 million, as of March 31, 2018 and December 31, 2017, respectively.

The entire disclosure for deferred revenues at the end of the reporting period, and description and amounts of significant changes that occurred during the reporting period. Deferred revenue is a liability as of the balance sheet date related to a revenue producing activity for which revenue has not yet been recognized. Generally, an entity records deferred revenue when it receives consideration from a customer before achieving certain criteria that must be met for revenue to be recognized in conformity with GAAP.