Summarizes Stock Appreciation Rights (SARs) Activity (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, beginning balance, Shares	1,530,845	1,674,534	1,943,176
Granted, Shares	862,000	524,534	605,000
Exercised, Shares	(112,875)	(571,723)	(731,142)
Forfeited, Shares	(176,500)	(96,500)	(142,500)
Stock Options Outstanding, ending balance, Shares	2,103,470	1,530,845	1,674,534
Exercisable, Ending Balance	675,152	439,561	632,034
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 27.46	$ 19.14	$ 12.19
Granted, Weighted-Average Exercise Price	40.87	41.97	30.15
Exercised, Weighted-Average Exercise Price	13.24	16.21	9.84
Forfeited, Weighted-Average Exercise Price	39.32	28.47	18.94
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	32.72	27.46	19.14
Exercisable, Weighted Average Exercise Price	$ 21.40	$ 12.18	$ 10.13
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 10 months 10 days	4 years 11 months 19 days	5 years 1 month 6 days
Exercisable, Weighted-Average Remaining Contractual Term	3 years 5 months 12 days	3 years 6 months 4 days	3 years 11 months 19 days
Outstanding, Aggregate Intrinsic Value	$ 12,265	$ 30,573	$ 29,886
Exercisable, Aggregate Intrinsic Value	$ 9,646	$ 15,480	$ 16,744
Stock Appreciation Rights (SARs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock Options Outstanding, beginning balance, Shares	1,049,850	1,060,250	495,000
Granted, Shares	244,000	259,600	754,000
Exercised, Shares	(18,750)	(167,500)	(68,750)
Forfeited, Shares	(30,500)	(102,500)	(120,000)
Stock Options Outstanding, ending balance, Shares	1,244,600	1,049,850	1,060,250
Exercisable, Ending Balance	424,992	153,575	35,000
Stock Options Outstanding, beginning balance, Weighted-Average Exercise Price	$ 34.61	$ 29.97	$ 19.19
Granted, Weighted-Average Exercise Price	40.64	43.97	34.70
Exercised, Weighted-Average Exercise Price	24.28	23.90	19.10
Forfeited, Weighted-Average Exercise Price	28.23	27.82	21.46
Stock Options Outstanding, ending balance, Weighted-Average Exercise Price	36.11	34.61	29.97
Exercisable, Weighted Average Exercise Price	$ 34.49	$ 38.12	$ 19.43
Stock Options Outstanding, Weighted-Average Remaining Contractual Term	4 years 9 months 18 days	5 years 5 months 16 days	6 years 1 month 10 days
Exercisable, Weighted-Average Remaining Contractual Term	4 years 4 months 21 days	5 years 7 months 2 days	5 years 6 months 11 days
Outstanding, Aggregate Intrinsic Value	$ 3,511	$ 13,425	$ 9,991
Exercisable, Aggregate Intrinsic Value	$ 2,315	$ 1,425	$ 602