Significant Accounting Policies - Additional Information (Detail) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) Project	Jun. 30, 2016 Project	Jun. 30, 2017 USD ($) Project Source Method	Jun. 30, 2016 Project	Dec. 31, 2016 USD ($)
Accounting Policies [Abstract]
Number of product revenue sources | Method			2
Unbilled receivables | $	$ 52.4		$ 52.4		$ 56.8
Number of projects | Project	6	6	7	10
Percentage of total revenues	16.00%	16.00%	14.00%	15.00%
Percentage of product revenues	20.00%	19.00%	18.00%	19.00%
Number of service revenue sources | Source			3