Summary of Stock Option Activity (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2014
Options
Beginning Balance (In Shares)	687,000
Granted (In Shares)	351,000	0	0
Exercised (In Shares)	(307,000)
Forfeited/expired (In Shares)	(107,000)
Ending Balance (In Shares)	624,000	687,000
Expected to Vest (In Shares)	323,000
Exercisable (In Shares)	289,000
Weighted Average Exercise Price
Beginning Balance (In Shares)	$ 15.95
Granted (In Shares)	$ 28.82
Exercised (In Shares)	$ 15.60
Forfeited/expired (In Shares)	$ 26.72
Ending Balance (In Shares)	$ 21.52	$ 15.95
Expected to Vest (In Shares)	$ 27.27
Exercisable (In shares)	$ 15.16
Weighted Average Remaining Contractual Term
Outstanding	6 years 7 months 10 days
Expected to Vest	8 years 11 months 16 days
Exercisable	4 years 14 days
Aggregate Intrinsic Value
Outstanding				$ 5,643
Expected	1,065
Exercisable	$ 4,449
Weighted Average Fair Value
Outstanding (In Dollars Per Share)	$ 8.35
Expected to Vest (In Dollars Per Share)	$ 9.81
Exercisable (In Dollars Per Share)	$ 6.60