Share-Based Compensation - Summary of Activity Related to Restricted Stock Granted under Incentive Plan (Detail) - Restricted Stock Grants [Member] shares in Thousands	9 Months Ended
	Sep. 30, 2015 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total Shares, Outstanding, Beginning Balance	1,033
Total Shares, Granted	324
Total Shares, Vested	(270)
Total Shares, Forfeited, canceled or expired	(15)
Total Shares, Outstanding, Ending Balance	1,072
Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 28.75
Weighted Average Grant Date Fair Value, Granted | $ / shares	45.66
Weighted Average Grant Date Fair Value, Vested | $ / shares	27.03
Weighted Average Grant Date Fair Value, Forfeited, cancelled or expired | $ / shares	29.60
Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 34.28