Acquisitions (Emtrol) - Additional Information (Detail) - Emtrol [Member] - USD ($) $ in Millions		12 Months Ended
	Nov. 03, 2014	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Equity interests acquired	100.00%
Consideration paid in cash for acquisition	$ 31.9
Shares issued for acquired subsidiary	453,858
Fair value of common stock issued	$ 5.8
Trading day period	30 days
Revenue from acquired entity		$ 33.4	$ 33.7	$ 9.8
Income from acquired entity		$ 4.5	$ 3.3	$ 1.3
Minimum [Member]
Business Acquisition [Line Items]
Restrictions on sale or transfer for periods range	1 year
Maximum [Member]
Business Acquisition [Line Items]
Restrictions on sale or transfer for periods range	2 years
Thirty Trading Days [Member]
Business Acquisition [Line Items]
Fair value of common stock issued	$ 6.0