Summarizes Stock Appreciation Rights (SARs) Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, beginning balance, Shares	1,674,534	1,943,176	2,129,929
Granted, Shares	524,534	605,000	510,000
Exercised, Shares	(571,723)	(731,142)	(672,753)
Forfeited, Shares	(96,500)	(142,500)	(24,000)
Stock Options Outstanding, ending balance, Shares	1,530,845	1,674,534	1,943,176
Exercisable, Ending Balance	439,561	632,034	1,055,176
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 19.14	$ 12.19	$ 8.82
Granted, Weighted-Average Exercise Price	41.97	30.15	19.64
Exercised, Weighted-Average Exercise Price	16.21	9.84	7.21
Forfeited, Weighted-Average Exercise Price	28.47	18.94	11.27
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	27.46	19.14	12.19
Exercisable, Weighted Average Exercise Price	$ 12.18	$ 10.13	$ 12.21
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 11 months 19 days	5 years 1 month 6 days	5 years 3 months 22 days
Exercisable, Weighted-Average Remaining Contractual Term	3 years 6 months 4 days	3 years 11 months 19 days	4 years 6 months 29 days
Outstanding, Aggregate Intrinsic Value	$ 30,573	$ 29,886	$ 28,379
Exercisable, Aggregate Intrinsic Value	$ 15,480	$ 16,744	$ 19,314
Stock Appreciation Rights (SARs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, beginning balance, Shares	1,060,250	495,000
Granted, Shares	259,600	754,000
Exercised, Shares	(167,500)	(68,750)
Forfeited, Shares	(102,500)	(120,000)
Stock Options Outstanding, ending balance, Shares	1,049,850	1,060,250	495,000
Exercisable, Ending Balance	153,575	35,000
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 29.97	$ 19.19
Granted, Weighted-Average Exercise Price	43.97	34.70
Exercised, Weighted-Average Exercise Price	23.90	19.10
Forfeited, Weighted-Average Exercise Price	27.82	21.46
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	34.61	29.97	$ 19.19
Exercisable, Weighted Average Exercise Price	$ 38.12	$ 19.43
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	5 years 5 months 16 days	6 years 1 month 10 days
Exercisable, Weighted-Average Remaining Contractual Term	5 years 7 months 2 days	5 years 6 months 11 days
Outstanding, Aggregate Intrinsic Value	$ 13,425	$ 9,991
Exercisable, Aggregate Intrinsic Value	$ 1,425	$ 602