Stockholder's Equity - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Stockholders' Equity Note [Abstract]
Common stock reserved and available for issuance	1,500,000
Common stock shares available for grant	379,063
Percentage of directors' stock grant vested on one year anniversary date	100.00%
Granted, Weighted average grant date fair value	$ 48.52
Share based award, settled in cash	1,300
Total unrecognized compensation cost related to nonvested shares of common stock granted	$ 17,900,000
Weighted average period of cost recognized	3 years 5 months 19 days
Total fair value of shares of common stock vested	$ 4,800,000
Compensation expense related to nonvested stock grants	$ 1,600,000	$ 1,000,000
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
Options issued	0
Options exercisable	0
Options exercised	0
Options forfeited	0
Options granted	0
Compensation expense related to stock options	$ 0
Shares redeemed to satisfy personal tax obligations	52,944
Treasury shares redeemed to pay income tax	$ 2,569,000
Director
Stockholders' Equity Note [Abstract]
Non vested stock grants to Independent director	11,700
Director Period of Vested Shares	1 year
Employee
Stockholders' Equity Note [Abstract]
Nonvested stock grants to employees	139,310
Period of Vested Shares	5 years