Consolidated Statements of Changes in Stockholders' Equity (USD $) In Thousands	Total	Common Stock Member	Additional Paid In Capital Member	Retained Earnings Member	Accumulated Other Comprehensive Income Member	Noncontrolling Interest Member
Balance at Dec. 31, 2008	$ 738,390	$ 464	$ 268,988	$ (54,693)	$ 670	$ 522,961
Balance (Share) at Dec. 31, 2008		46,342
Offering cost	(42)	0	(42)	0	0	0
Conversion of restricted stock, net of shares withheld for taxes	(354)	0	(354)	0	0	0
Conversion of restricted stock, net of shares withheld for taxes (Shares)		182
Stock-based compensation	8,855	0	3,077	0	0	5,778
Common dividends paid	(4,228)	0	0	(4,228)	0	0
Net income (loss)	86,105	0	0	15,642	0	70,463
Hedging gains or losses reclassified to earnings	(2,087)	0	0	0	(550)	(1,537)
Adjustment in fair value of derivatives	(2,964)	0	0	0	(688)	(2,276)
Distribution to non-controlling interest	(7,765)	0	0	0	0	(7,765)
Balance at Dec. 31, 2009	815,910	464	271,669	(43,279)	(568)	587,624
Balance (Share) at Dec. 31, 2009		46,524
Issuance of units by the Partnership to non-controlling interest	120,786	0	0	0	0	120,786
Conversion of restricted stock, net of shares withheld for taxes	(705)	4	(709)	0	0	0
Conversion of restricted stock, net of shares withheld for taxes (Shares)		370
Change in equity due to issuance of units by the Partnership	(68)	0	(32,769)	0	115	32,586
Stock-based compensation	9,569	0	4,199	0	0	5,370
Common dividends paid	(3,368)	0	0	(3,368)	0	0
Net income (loss)	(21,513)	0	0	(11,651)	0	(9,862)
Hedging gains or losses reclassified to earnings	1,877		0	0	353	1,524
Adjustment in fair value of derivatives	(249)			0	(45)	(204)
Non-controlling partner's impact of conversion of restricted units and options exercise	(1,768)	0	0	0	0	(1,768)
Distribution to non-controlling interest	(18,993)	0	0	0	0	(18,993)
Balance at Dec. 31, 2010	901,478	468	242,390	(58,298)	(145)	717,063
Balance (Share) at Dec. 31, 2010		46,894
Conversion of restricted stock, net of shares withheld for taxes	(1,068)	3	(1,071)	0	0	0
Conversion of restricted stock, net of shares withheld for taxes (Shares)		300
Change in equity due to issuance of units by the Partnership	(476)	0	(476)	0	0	0
Stock-based compensation	7,556	0	3,368	0	0	4,188
Common dividends paid	(17,872)	0	0	(17,872)	0	0
Net income (loss)	(1,279)	0	0	(6,007)	0	4,728
Hedging gains or losses reclassified to earnings	1,769	0	0	0	330	1,439
Adjustment in fair value of derivatives	(1,446)	0	0	0	(270)	(1,176)
Non-controlling partner's impact of conversion of restricted units and options exercise	(1,206)				(1,206)
Distribution to non-controlling interest	(58,209)	0	0	0	0	(58,209)
Balance at Dec. 31, 2011	$ 829,247	$ 471	$ 244,211	$ (82,177)	$ (85)	$ 666,827
Balance (Share) at Dec. 31, 2011		47,194