Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Stockholders' Equity Note [Abstract]
Common stock available for issuance	1,500,000
Common stock shares available for grant	491,037
Percentage of directors' stock grant vested on one year anniversary date	100.00%
Period of Vested Shares		5 years
Granted, Weighted average grant date fair value	$ 34.06	$ 34.06
Share based award, settled in cash	1,800
Total unrecognized compensation cost related to nonvested shares of common stock granted	$ 10,500
Weighted average period of cost recognized	3 years 1 month 12 days
Total fair value of shares of common stock vested	$ 4,100	$ 3,900
Compensation expense related to nonvested stock grants	$ 3,200	$ 3,100
Price of shares issued under Employee Stock Purchase Plan as a percentage of FMV	95.00%
Number of shares reserved for the Employee Stock Purchase Plan	250,000
Additional shares authorized for issuance	250,000
Stock options exercised, Shares	9,500
Options, Weighted Average Exercise Price	$ 15.21
Options granted	0
Options outstanding	5,500
Options, Outstanding, Weighted Average Exercise Price	$ 19.75
Shares redeemed to satisfy personal tax obligations	41,550
Treasury shares redeemed to pay income tax	$ 1,449
Options forfeited	0
Director
Stockholders' Equity Note [Abstract]
Non vested stock grants to Independent director	16,200
Director Period of Vested Shares	1 year
Employee
Stockholders' Equity Note [Abstract]
Nonvested stock grants to employees	182,865