Earnings per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Weighted average number of shares for calculation of basic EPS – Common Stock	36,448,138	36,031,792	35,411,608
Stock options under equity incentive plans	152,665	443,310	637,723
Weighted average number of shares for calculation of diluted EPS – Common Stock	36,600,803	36,475,102	36,049,331
Stock options outstanding for equity incentive plans
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Common stock that have been excluded from the diluted shares calculation	1,314,784	17,534	155,000