Calculation of Earnings Per Share - Calculation of Basic and Diluted Earnings Per Share (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Calculation of Basic Earnings Per Share:
Net Income	$ 3,180	$ 3,879	$ 25,995	$ 23,104	$ 32,787
Weighted shares outstanding - Basic (in shares)	14,574,678	14,438,152	14,539,841	14,424,404
Basic Earnings Per Share (in usd per share)	$ 0.22	$ 0.27	$ 1.79	$ 1.60
Reconciliation of Numerator:
Net Income	3,180	3,879	25,995	23,104	32,787
Effect of 8.25% Convertible debentures	0	11	0	33
Adjusted numerator-Diluted	$ 3,180	$ 3,890	$ 25,995	$ 23,137
Reconciliation of Denominator:
Weighted shares outstanding - Basic (in shares)	14,574,678	14,438,152	14,539,841	14,424,404
Effect of dilutive securities:
Share-based Compensation (in shares)	41,987	39,185	48,289	35,832
8.25% Convertible debentures (in shares)	0	76,164	0	78,231
Adjusted denominator-Diluted (in shares)	14,616,665	14,553,501	14,588,130	14,538,467
Diluted Earnings Per Share (in usd per share)	$ 0.22	$ 0.27	$ 1.78	$ 1.59