Calculation of Earnings Per Share (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Dec. 31, 2011
Calculation of Basic Earnings Per Share:
Net Income	$ 3,219	$ 2,397	$ 19,006	$ 19,664	$ 27,622
Weighted average shares outstanding	9,592,417	9,564,012	9,583,316	9,552,472
Basic Earnings Per Share	$ 0.34	$ 0.25	$ 1.98	$ 2.06
Reconciliation of Numerator:
Net Income	3,219	2,397	19,006	19,664	27,622
Effect of 8.25% Convertible debentures	13	15	41	46
Adjusted numerator - Diluted	$ 3,232	$ 2,412	$ 19,047	$ 19,710
Reconciliation of Denominator:
Weighted shares outstanding - Basic	9,592,417	9,564,012	9,583,316	9,552,472
Effect of dilutive securities:
Share-based Compensation	23,770	23,925	22,684	22,623
8.25% Convertible debentures	60,471	70,033	67,681	72,537
Adjusted denominator - Diluted	9,676,658	9,657,970	9,673,681	9,647,632
Diluted Earnings Per Share	$ 0.33	$ 0.25	$ 1.97	$ 2.04