Summary of Significant Accounting Policies (Detail) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017 USD ($) unit	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($) unit measurement	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash	$ 1,020		$ 1,020		$ 6,020
Unbilled receivables, current	5,296		5,296		6,755
Billings in excess of cost, current	2,374		2,374		$ 1,730
Provision for losses on contracts	262		262
Building impairment	$ 2,965	$ 0	$ 2,965	$ 0
Number of units with APC technology (in units) | unit	1,000		1,000
Minimum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract term (in months)			8 months
Critical operational measurements (in measurements) | measurement			3
Maximum
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Contract term (in months)			16 months
Critical operational measurements (in measurements) | measurement			4