Equity Compensation Plans (Summary of Option Activity) (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compensation and Retirement Disclosure [Abstract]
Shares Outstanding, Beginning balance	758,000
Shares granted	131,800	75,279	146,500
Shares Exercised	(277,006)	(158,322)	(129,675)
Shares Forfeited/Cancelled	(4,000)
Shares Outstanding, Ending balance	609,000	758,000
Shares Options exercisable	321,000
Shares Expected to vest	261,000
Weighted-Average Exercise Price Outstanding, Beginning balance	$ 10.32
Weighted-Average Exercise Price Granted	$ 27.96
Weighted-Average Exercise Price Exercised	$ 8.87
Weighted-Average Exercise Price Forfeited/Cancelled	$ 9.24
Weighted-Average Exercise Price Outstanding, Ending balance	$ 14.81	$ 10.32
Weighted-Average Exercise Price Options exercisable	$ 9.99
Weighted-Average Exercise Price Expeceted to vest	$ 19.78
Weighted average remaining contractual term	7 years
Weighted Average Remaing Contractual Term Options exercisable	5 years 2 months 12 days
Weighted Average Remaining Contractual Term Expected to Vest	8 years 10 months 24 days
Aggregate Intrinsic Value Outstanding	$ 10,967
Aggregate Intrinsic Value Options exercisable	7,323
Aggregate Instrinsic Value Options Expected to Vest	$ 3,408