Consolidated Statements of Changes in Partners' Equity (USD $) In Thousands, except Share data	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Noncontrolling Interest [Member]
Balance, at Dec. 31, 2009	$ 815,910	$ 464	$ 271,669	$ (43,279)	$ (568)	$ 587,624
Balance (Shares) 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
Changes 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 loss	(21,513)	0	0	(11,651)	0	(9,862)
Hedging gains or losses reclassified to earnings	1,877	0	0	0	353	1,524
Adjustment in fair value of derivatives	(249)	0	0	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 (Shares) 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
Changes 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 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)	0	0	0	0	(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 (Shares) at Dec. 31, 2011		47,194
Issuance of units by the Partnership to non-controlling interest	232,791	0	0	0	0	232,791
Conversion of restricted stock, net of shares withheld for taxes	(794)	2	(796)	0	0	0
Conversion of restricted stock, net of shares withheld for taxes (Shares)		220
Changes in equity due to issuance of units by the Partnership	8,610	0	24,500	0	0	(15,890)
Stock-based compensation	9,483	0	4,481	0	0	5,002
Common dividends paid	(22,925)	0	0	(22,925)	0	0
Net loss	(36,740)	0	0	(12,481)	0	(24,259)
Hedging gains or losses reclassified to earnings	(641)	0	0	0	(81)	(560)
Adjustment in fair value of derivatives	1,642	0	0	0	307	1,335
Non-controlling partner's impact of conversion of restricted units and options exercise	(594)	0	0	0	0	(594)
Distribution to non-controlling interest	(69,839)	0	0	0	0	(69,839)
Purchase of non-controlling interest	0	0	2,239	0	0	(2,239)
Balance, at Dec. 31, 2012	$ 950,240	$ 473	$ 274,635	$ (117,583)	$ 141	$ 792,574
Balance (Shares) at Dec. 31, 2012		47,414