Stock-Based Compensation - Reconciliation of Outstanding Balance of Stock Options (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Outstanding at beginning	530		601
Options granted	0	0	0	0
Options exercised	(20)		(91)
Options forfeited or expired	0		0
Outstanding at ending	510		510
Exercisable at ending	510		510
Weighted Average Exercise Price at beginning	$ 17.12		$ 16.97
Weighted Average Exercise Price, Options granted	0		0
Weighted Average Exercise Price, Options exercised	9.64		14.47
Weighted Average Exercise Price, Options forfeited or expired	0		0
Weighted Average Exercise Price at ending	17.41		17.41
Weighted Average Exercise Price, Exercisable at ending	17.41		17.41
Weighted Average Grant Date Fair Value at beginning	8.51		8.42
Weighted Average Grant Date Fair Value, Options granted	0		0
Weighted Average Grant Date Fair Value, Options exercised	6.30		7.46
Weighted Average Grant Date Fair Value, Options forfeited or expired	0		0
Weighted Average Grant Date Fair Value at ending	8.59		8.59
Weighted Average Grant Date Fair Value, Exercisable at ending	$ 0		$ 0
Aggregate Intrinsic Value Outstanding at ending	$ 6,699		$ 6,699
Aggregate Intrinsic Value, Exercisable at ending	$ 6,699		$ 6,699