Stock Incentive Plans - Summary of Restricted Stock Activity (Detail) - Restricted Stock $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) grant $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares	Dec. 31, 2014 USD ($) $ / shares shares
Number of Restricted Stock
Outstanding as of beginning of period (in shares) | shares	1,293	982	811
Granted (in shares) | shares	1,048	556	528
Forfeited/Canceled (in shares) | shares	(353)	(59)	(84)
Vested (in shares) | shares	(280)	(186)	(273)
Outstanding as of end of period (in shares) | shares	1,708	1,293	982
Weighted Average Grant Date Fair Value
Outstanding as of beginning of period (in dollars per share) | $ / shares	$ 20.89	$ 18.55	$ 16.89
Granted (in dollars per share) | $ / shares	22.46	24.01	20.18
Forfeited/Canceled (in dollars per share) | $ / shares	21.04	19.37	18.38
Vested (in dollars per share) | $ / shares	20.67	18.28	17.37
Outstanding as of end of period (in dollars per share) | $ / shares	$ 21.86	$ 20.89	$ 18.55
Total Intrinsic Value of Restricted Stock Vested
Vested | $	$ 6,434	$ 4,580	$ 5,624
Number of annual grants | grant	2