Stockholder's Equity - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Stockholders' Equity Note [Abstract]
Common stock reserved and available for issuance	1,500,000
Common stock shares available for grant	259,937
Percentage of directors' stock grant vested on one year anniversary date	100.00%
Granted, Weighted average grant date fair value	$ 38.01
Share based award, settled in cash	1,700
Total unrecognized compensation cost related to nonvested shares of common stock granted	$ 13,000
Weighted average period of cost recognized	3 years 3 months 7 days
Total fair value of shares of common stock vested	$ 4,500
Compensation expense related to nonvested stock grants	$ 3,500	$ 3,200
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	5,500
Options, weighed average exercise price	$ 19.75
Options granted	0
Options forfeited	0
Options outstanding	0
Shares redeemed to satisfy personal tax obligations	50,312
Treasury shares redeemed to pay income tax	$ 1,931
Employee
Stockholders' Equity Note [Abstract]
Nonvested stock grants to employees	215,800
Employee Period of Vested Shares	5 years
Director
Stockholders' Equity Note [Abstract]
Nonvested stock grants to Independent directors	15,300
Director Period of Vested Shares	1 year