Consolidated Condensed Statements of Stockholders' Equity (Unaudited) - USD ($) $ in Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Total
Balance (in shares) at Dec. 31, 2014	33,419,000
Balance at Dec. 31, 2014	$ 334	$ 87,370	$ 300,222	$ 387,926
Net income			26,955	26,955
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	204,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 2	2,361		2,363
Tax benefits from share-based payment arrangement exercises		451		451
Share-based payment arrangement compensation expense		1,189		1,189
Dividends on common stock			(2,518)	(2,518)
Balance (in shares) at Sep. 30, 2015	33,623,000
Balance at Sep. 30, 2015	$ 336	91,371	324,659	416,366
Net income			8,790	8,790
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	78,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 1	1,126		1,127
Share-based payment arrangement compensation expense		215		215
Dividends on common stock			(824)	(824)
Balance (in shares) at Dec. 31, 2015	32,760,000
Balance at Dec. 31, 2015	$ 328	76,468	332,625	$ 409,421
Repurchase and retirement of common stock (in shares)	(941,000)			(941,024)
Repurchase and retirement of common stock	$ (9)	(16,166)		$ (16,175)
Tax deficiencies from share-based payment arrangement exercises		(78)		(78)
Repurchase and retirement of common stock	$ (9)	(16,166)		(16,175)
Net income			25,161	25,161
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in shares)	267,000
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	$ 3	3,505		3,508
Share-based payment arrangement compensation expense		741		741
Dividends on common stock			(2,436)	(2,436)
Balance (in shares) at Sep. 30, 2016	32,571,000
Balance at Sep. 30, 2016	$ 326	73,024	355,350	428,700
Repurchase and retirement of common stock (in shares)	(456,000)
Repurchase and retirement of common stock	$ (5)	(7,508)		(7,513)
Tax deficiencies from share-based payment arrangement exercises		(55)		(55)
Repurchase and retirement of common stock	$ (5)	(7,508)		(7,513)
Employee taxes paid in exchange for shares withheld		$ (127)		$ (127)