Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement of Cash Flows [Abstract]
Net loss	$ (36,740)	$ (1,279)	$ (21,513)
Adjustments to reconcile net loss to net cash provided by
Depreciation and amortization	162,300	125,358	111,625
Non-cash stock-based compensation	9,483	7,556	9,569
(Gain) loss on sale of property	(3,328)	264	(13,881)
Impairments	0	0	1,311
Deferred tax (benefit) expense	(8,384)	(4,540)	(7,538)
Derivatives mark to market interest rate settlement	0	0	(24,160)
Non-cash portion of derivatives loss	(3,508)	761	1,136
Non-cash portion of loss on debt extinguishment	0	0	5,396
Interest paid-in-kind	0	0	(11,558)
Amortization of debt issue costs	5,377	6,462	6,680
Amortization of discount on notes	1,897	1,897	1,686
Equity in income of limited liability company	(3,250)	0	0
Changes in assets and liabilities:
Accounts receivable, accrued revenue and other	(39,120)	44,121	4,665
Natural gas and natural gas liquids, prepaid expenses and other	(4,015)	(1,507)	2,376
Accounts payable, accrued gas purchases and other accrued liabilities	19,744	(37,800)	18,996
Net cash provided by operating activities	100,456	141,293	84,790
Cash flows from investing activities:
Additions to property and equipment	(234,849)	(97,572)	(48,191)
Insurance recoveries on property and equipment	0	0	2,599
Acquisitions and asset purchases	(214,957)	0	0
Proceeds from sale of property	11,773	478	60,230
Investment in limited liability company	(52,250)	(35,000)	0
Net cash provided by (used in) investing activities	(490,283)	(132,094)	14,638
Cash flows from financing activities:
Proceeds from borrowings	806,500	471,250	997,412
Payments on borrowings	(570,500)	(393,308)	(1,144,705)
Payments on capital lease obligations	(3,112)	(3,122)	(2,385)
Increase (decrease) in drafts payable	(1,912)	5,854	(5,063)
Debt refinancing costs	(7,155)	(3,954)	(28,561)
Distributions to non-controlling interest	(69,839)	(58,209)	(18,993)
Common dividends paid	(22,925)	(17,872)	(3,368)
Conversion of restricted units, net of units withheld for taxes	(1,030)	(1,798)	(2,659)
Conversion of restricted stock, net of shares withheld for taxes	(794)	(1,068)	(705)
Proceeds from issuance of preferred units	232,791	0	120,786
Proceeds from exercise of unit options	436	591	890
Net cash provided by (used in) financing activities continuing operations	362,460	(1,636)	(87,351)
Net increase (decrease) in cash and cash equivalents	(27,367)	7,563	12,077
Cash and cash equivalents, beginning of period	30,343	22,780	10,703
Cash and cash equivalents, end of period	2,976	30,343	22,780
Cash paid for interest	81,237	71,950	66,081
Cash paid for income taxes	$ 1,706	$ 1,104	$ (33)