Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Statement of Cash Flows [Abstract]
Net income (loss)	$ (16,515)	$ 568
Adjustments to reconcile net income (loss) to net cash provided by operating activities
Depreciation and amortization	68,417	65,085
Gain (loss) on sale of property and other assets	95	(504)
Deferred tax benefit	(9,654)	(1,871)
Non-cash stock-based compensation	8,137	5,113
Non-cash portion of derivatives gain	(287)	(5,975)
Distribution of earnings from limited liability company	3,209	0
Amortization of debt issue costs	3,150	1,321
Amortization of discount on notes	948	948
Changes in assets and liabilities:
Accounts receivable, accrued revenue and other	18,464	24,991
Natural gas and natural gas liquids, prepaid expenses and other	(9,619)	(8,971)
Accounts payable, accrued gas and crude oil purchases and other accrued liabilities	(4,413)	(29,300)
Net cash provided by operating activities	61,932	51,405
Cash flows from investing activities:
Additions to property and equipment	(288,094)	(90,046)
Proceeds from sale of property	18,072	632
Investment in limited liability company	(17,609)	(52,250)
Distribution from limited liability company in excess of earnings	5,546	0
Net cash used in investing activities	(282,085)	(141,664)
Cash flows from financing activities:
Proceeds from borrowings	222,912	548,500
Payments on borrowings	(267,500)	(335,500)
Increase in restricted cash	0	(245,100)
Payments on capital lease obligations	(1,625)	(1,536)
Increase (decrease) in drafts payable	775	(5,985)
Debt refinancing costs	(2,764)	(4,962)
Conversion of restricted stock, net of shares withheld for taxes	(1,196)	(629)
Distributions to non-controlling partners in the Partnership	(41,856)	(32,583)
Contributions from non-controlling partners	2,169	0
Common dividend paid	(11,748)	(11,221)
Issuance of common units by the Partnership	362,778	158,014
Conversion of restricted units, net of units withheld for taxes	(1,261)	(980)
Proceeds from exercise of Partnership unit options	617	95
Net cash provided by financing activities	261,301	68,113
Net decrease in cash and cash equivalents	41,148	(22,146)
Cash and cash equivalents, beginning of period	2,976	30,343
Cash and cash equivalents, end of period	44,124	8,197
Cash paid for interest	44,314	36,252
Cash paid for income taxes	$ 4,698	$ 784