Incentive Plan - Summary of Stock Options Outstanding (Detail)	12 Months Ended
	Dec. 31, 2015 $ / shares shares
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Options Outstanding | shares	2,281,931
Weighted Average Remaining Contractual Life, Options Outstanding	5 years
Weighted Average Exercise Price, Options Outstanding	$ 17.62
Number Of Options Exercisable | shares	1,497,960
Weighted Average Remaining Contractual Life, Options Exercisable	3 years 6 months
Weighted Average Exercise Price, Options Exercisable	$ 17.96
Exercise Prices From 10.00 to 12.28 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Prices Lower Limit	10.00
Exercise Prices Higher Limit	$ 12.28
Number of Options Outstanding | shares	279,561
Weighted Average Remaining Contractual Life, Options Outstanding	3 years 10 months 24 days
Weighted Average Exercise Price, Options Outstanding	$ 10.59
Number Of Options Exercisable | shares	279,561
Weighted Average Remaining Contractual Life, Options Exercisable	3 years 10 months 24 days
Weighted Average Exercise Price, Options Exercisable	$ 10.59
Exercise Prices From 13.83 to 14.62 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Prices Lower Limit	13.83
Exercise Prices Higher Limit	$ 14.62
Number of Options Outstanding | shares	664,650
Weighted Average Remaining Contractual Life, Options Outstanding	6 years 2 months 12 days
Weighted Average Exercise Price, Options Outstanding	$ 14.13
Number Of Options Exercisable | shares	393,400
Weighted Average Remaining Contractual Life, Options Exercisable	6 years
Weighted Average Exercise Price, Options Exercisable	$ 14.05
Exercise Prices From 16.06 to 18.45 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Prices Lower Limit	16.06
Exercise Prices Higher Limit	$ 18.45
Number of Options Outstanding | shares	724,860
Weighted Average Remaining Contractual Life, Options Outstanding	6 years 9 months 18 days
Weighted Average Exercise Price, Options Outstanding	$ 17.37
Number Of Options Exercisable | shares	257,055
Weighted Average Remaining Contractual Life, Options Exercisable	3 years 2 months 12 days
Weighted Average Exercise Price, Options Exercisable	$ 17.07
Exercise Prices From 20.25 to 23.48 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Prices Lower Limit	20.25
Exercise Prices Higher Limit	$ 23.48
Number of Options Outstanding | shares	312,860
Weighted Average Remaining Contractual Life, Options Outstanding	7 months 6 days
Weighted Average Exercise Price, Options Outstanding	$ 22.57
Number Of Options Exercisable | shares	312,860
Weighted Average Remaining Contractual Life, Options Exercisable	7 months 6 days
Weighted Average Exercise Price, Options Exercisable	$ 22.57
Exercise Prices 27.34 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Exercise Prices Lower Limit	$ 27.34
Number of Options Outstanding | shares	300,000
Weighted Average Remaining Contractual Life, Options Outstanding	3 years 4 months 24 days
Weighted Average Exercise Price, Options Outstanding	$ 27.34
Number Of Options Exercisable | shares	255,084
Weighted Average Remaining Contractual Life, Options Exercisable	3 years 3 months 18 days
Weighted Average Exercise Price, Options Exercisable	$ 27.34