Consolidated Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2013	33,301
Balance at Dec. 31, 2013	$ 333,000	$ 85,077,000	$ 273,727,000	$ 359,137,000
Net income			$ 20,865,000	20,865,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	105
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 1,000	$ 1,054,000		1,055,000
Tax benefits from share-based payment arrangement exercises		141,000		141,000
Share-based payment arrangement compensation expense		$ 720,000		720,000
Dividends on common stock			$ (2,504,000)	(2,504,000)
Balance (in shares) at Sep. 30, 2014	33,406
Balance at Sep. 30, 2014	$ 334,000	$ 86,992,000	292,088,000	379,414,000
Net income			$ 8,969,000	8,969,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	13
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards		$ 159,000		159,000
Tax benefits from share-based payment arrangement exercises		18,000		18,000
Share-based payment arrangement compensation expense		$ 201,000		201,000
Dividends on common stock			$ (835,000)	(835,000)
Balance (in shares) at Dec. 31, 2014	33,419
Balance at Dec. 31, 2014	$ 334,000	$ 87,370,000	300,222,000	387,926,000
Net income			$ 26,955,000	26,955,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	204
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 2,000	$ 2,361,000		2,363,000
Tax benefits from share-based payment arrangement exercises		451,000		451,000
Share-based payment arrangement compensation expense		$ 1,189,000		1,189,000
Dividends on common stock			$ (2,518,000)	(2,518,000)
Balance (in shares) at Sep. 30, 2015	33,623
Balance at Sep. 30, 2015	$ 336,000	$ 91,371,000	$ 324,659,000	$ 416,366,000