Consolidated Statements Of Changes In Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Voting Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]	Treasury Stock [Member]	Total
Balance at Dec. 31, 2008	$ 216	$ 348	$ 6,072	$ 1,964	$ (141)	$ 8,459
Balance, shares at Dec. 31, 2008	21,592,462
Stock-based compensation		1,411				1,411
Vesting of non-vested shares, shares	19,245
Comprehensive income:
Net income			21,835			21,835
Change in postretirement benefit obligations, net of tax (Note 15)				(301)		(301)
Total comprehensive income						21,534
Balance at Dec. 31, 2009	216	1,759	27,907	1,663	(141)	31,404
Balance, shares at Dec. 31, 2009	21,611,707
Stock-based compensation		1,651				1,651
Exercise of stock options		64				64
Exercise of stock options, shares	15,422
Vesting of non-vested shares, shares	5,273
Comprehensive income:
Net income			11,916			11,916
Change in postretirement benefit obligations, net of tax (Note 15)				(128)		(128)
Total comprehensive income						11,788
Balance at Dec. 31, 2010	216	3,474	39,823	1,535	(141)	44,907
Balance, shares at Dec. 31, 2010	21,632,402
Stock-based compensation		2,779				2,779
Exercise of stock options	1	550				551
Exercise of stock options, shares	97,376
Vesting of non-vested shares	1	151				152
Vesting of non-vested shares, shares	20,459
Comprehensive income:
Net income			11,218			11,218
Change in valuation of interest rate swap, net of tax (Note 7)				(68)		(68)
Change in postretirement benefit obligations, net of tax (Note 15)				(382)		(382)
Total comprehensive income						10,768
Balance at Dec. 31, 2011	$ 218	$ 6,954	$ 51,041	$ 1,085	$ (141)	$ 59,157
Balance, shares at Dec. 31, 2011	21,750,237