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 December 31, 2009 at Dec. 31, 2009	$ 219	$ 76,477	$ 196,480	$ 1,731	$ 274,907
Balance at December 31, 2009 (in Shares) at Dec. 31, 2009	21,885
Net income			19,742		19,742
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	1	302			303
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	65
Tax benefits from share-based payment arrangement exercises		385			385
Share-based payment arrangement compensation expense		1,264			1,264
Dividends on common stock			(877)		(877)
Income before income taxes attributable to noncontrolling interest				631	631
Noncontrolling interest distributions				(451)	(451)
Balance at Dec. 31, 2010	220	78,428	215,345	1,911	295,904
Balance (in Shares) at Dec. 31, 2010	21,950
Net income			24,285		24,285
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards		137			137
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	35
Tax benefits from share-based payment arrangement exercises		164			164
Share-based payment arrangement compensation expense		1,349			1,349
Dividends on common stock			(1,758)		(1,758)
Income before income taxes attributable to noncontrolling interest				807	807
Noncontrolling interest distributions				(529)	(529)
Balance at Dec. 31, 2011	220	80,078	237,872	2,189	320,359
Balance (in Shares) at Dec. 31, 2011	21,985
Net income			27,267		27,267
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards	1	967			968
Issuance of common stock from share-based payment arrangement exercises and vesting of performance unit awards (in Shares)	125
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	$ 221	$ 82,679	$ 246,460	$ 2,563	$ 331,923
Balance (in Shares) at Dec. 31, 2012	22,110