New Accounting Standards - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
ASU 2016-09
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Increase in provision for income taxes	$ 2.1	$ 2.0	$ 1.5