Equity and Changes in Equity During Period (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015	Dec. 31, 2014
Equity [Abstract]
Balance at beginning of period			$ 877,596
Net income	$ 13,182	$ 6,867	35,920	$ 26,789
Currency translation	(245)	$ (266)	(1,037)	$ (163)
Stock-based compensation			19,175
Repurchases of common stock			(14,774)
Shares repurchased and retired to satisfy tax withholding upon vesting			(1,205)
Tax benefit related to stock-based compensation			22,114		$ 27,800	$ 13,000
Stock option exercises, net of withholdings and other			11,814
Balance at end of period	$ 949,603		$ 949,603		$ 877,596