Consolidated Condensed Statements of Stockholders Equity (Unaudited) (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2011	$ 220	$ 80,078	$ 237,872	$ 2,189	$ 320,359
Balance (in Shares) at Dec. 31, 2011	21,985
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	1	540			541
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	73
Tax benefits from share-based payment arrangement exercises		272			272
Share-based payment arrangement compensation expense		248			248
Dividends on common stock			(441)		(441)
Income before income taxes attributable to noncontrolling interest				161	161
Noncontrolling interest distributions				(104)	(104)
Net income			5,446		5,446
Balance at Mar. 31, 2012	221	81,138	242,877	2,246	326,482
Balance (in Shares) at Mar. 31, 2012	22,058
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards		427			427
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	52
Tax benefits from share-based payment arrangement exercises		137			137
Share-based payment arrangement compensation expense		977			977
Dividends on common stock			(18,238)		(18,238)
Income before income taxes attributable to noncontrolling interest				336	336
Noncontrolling interest distributions				(19)	(19)
Net income			21,821		21,821
Balance at Dec. 31, 2012	221	82,679	246,460	2,563	331,923
Balance (in Shares) at Dec. 31, 2012	22,110
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards		22			22
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	12
Share-based payment arrangement compensation expense		217			217
Dividends on common stock			(553)		(553)
Income before income taxes attributable to noncontrolling interest				84	84
Noncontrolling interest distributions				(84)	(84)
Change to equity method of accounting				(2,563)	(2,563)
Net income			7,202		7,202
Balance at Mar. 31, 2013	$ 221	$ 82,918	$ 253,109		$ 336,248
Balance (in Shares) at Mar. 31, 2013	22,122