Consolidated Statements of Stockholders' Equity (USD $) In Thousands	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Noncontrolling Interest [Member]	Total
Balance at Dec. 31, 2011	$ 330	$ 80,078	$ 237,762	$ 2,189	$ 320,359
Balance (in Shares) at Dec. 31, 2011	32,977
Net income			27,267		27,267
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	2	967	(1)		968
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	187
Tax benefits from share-based payment arrangement exercises		409			409
Share-based payment arrangement compensation expense		1,225			1,225
Dividends on common stock			(18,679)		(18,679)
Income before income taxes attributable to noncontrolling interest				497	497
Noncontrolling interest distributions				(123)	(123)
Balance at Dec. 31, 2012	332	82,679	246,349	2,563	331,923
Balance (in Shares) at Dec. 31, 2012	33,164
Net income			30,147		30,147
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	1	1,125			1,126
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	137
Tax benefits from share-based payment arrangement exercises		189			189
Share-based payment arrangement compensation expense		1,084			1,084
Dividends on common stock			(2,769)		(2,769)
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)
Balance at Dec. 31, 2013	333	85,077	273,727		359,137
Balance (in Shares) at Dec. 31, 2013	33,301
Net income			29,834		29,834
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	1	1,213			1,214
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	118
Tax benefits from share-based payment arrangement exercises		159			159
Share-based payment arrangement compensation expense		921			921
Dividends on common stock			(3,339)		(3,339)
Balance at Dec. 31, 2014	$ 334	$ 87,370	$ 300,222		$ 387,926
Balance (in Shares) at Dec. 31, 2014	33,419