Consolidated Statement of Changes in Equity (USD $) In Thousands, unless otherwise specified	Total	Partners' Equity, Total [Member]	Common Equity [Member]	Preferred Equity [Member]	Limited Partners' Common Equity [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Non-controlling Interest [Member]
Balance at Dec. 31, 2008	$ 2,899,758	$ 2,895,810	$ 1,840,002	$ 1,016,625	$ 47,835	$ (8,652)	$ 3,948
Comprehensive income (loss):
Net income (loss)	(271,490)	(271,249)	(333,601)	73,451	(11,099)		(241)
Derivative instrument activity	3,022	3,022				3,022
Comprehensive income (loss)	(268,468)	(268,227)					(241)
Issuance of Limited Partner Units for acquisition	0
Capital Contribution from the General Partner	551,404	551,404	551,404
Stock based compensation plan activity	11,337	11,337	11,337
Conversion of Limited Partner Units to common shares of the General Partner			577		(577)
Distribution to Preferred Unitholders	(73,451)	(73,451)		(73,451)
Distributions to partners	(156,357)	(156,357)	(151,390)		(4,967)
Contributions from (distributions to) noncontrolling interests, net	3,443						3,443
Balance at Dec. 31, 2009	2,967,666	2,960,516	1,918,329	1,016,625	31,192	(5,630)	7,150
Comprehensive income (loss):
Net income (loss)	65,262	65,447	(3,670)	69,468	(351)		(185)
Derivative instrument activity	4,198	4,198				4,198
Comprehensive income (loss)	69,460	69,645					(185)
Issuance of Limited Partner Units for acquisition	0
Capital Contribution from the General Partner	298,066	298,066	298,066
Stock based compensation plan activity	10,528	10,528	10,528
Conversion of Limited Partner Units to common shares of the General Partner			(8,055)		8,055
Distribution to Preferred Unitholders	(69,468)	(69,468)		(69,468)
Redemption/repurchase of Preferred Units	(118,787)	(118,787)	(6,702)	(112,085)
Distributions to partners	(165,881)	(165,881)	(161,879)		(4,002)
Contributions from (distributions to) noncontrolling interests, net	(1,739)						(1,739)
Balance at Dec. 31, 2010	2,989,845	2,984,619	2,046,617	904,540	34,894	(1,432)	5,226
Comprehensive income (loss):
Net income (loss)	96,309	96,424	35,212	60,353	859		(115)
Derivative instrument activity	2,419	2,419				2,419
Comprehensive income (loss)	98,728	98,843					(115)
Issuance of Limited Partner Units for acquisition	28,357	28,357			28,357
Stock based compensation plan activity	10,890	10,890	10,890
Conversion of Limited Partner Units to common shares of the General Partner			3,130		(3,130)
Distribution to Preferred Unitholders	(60,353)	(60,353)		(60,353)
Redemption/repurchase of Preferred Units	(110,726)	(110,726)	(96)	(110,630)
Distributions to partners	(176,593)	(176,593)	(171,867)		(4,726)
Contributions from (distributions to) noncontrolling interests, net	(566)						(566)
Balance at Dec. 31, 2011	$ 2,779,582	$ 2,775,037	$ 1,923,886	$ 793,910	$ 56,254	$ 987	$ 4,545
Common Units outstanding at Dec. 31, 2011		259,872	252,927		6,945