Consolidated Statements of Cash Flows - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Statement of Cash Flows [Abstract]
Net income (loss)	$ (870.1)	$ 69.6
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Impairments	873.3	0.0
Depreciation and amortization	246.8	189.0
Accretion expense	0.2	0.3
Loss on disposition of assets	0.1	0.0
Deferred tax (benefit) expense	(0.6)	17.8
Non-cash unit-based compensation	15.4	21.5
(Gain) loss on derivatives recognized in net income (loss)	6.1	(5.0)
Cash settlements on derivatives	8.3	11.3
Amortization of debt issue costs	1.9	1.5
Amortization of net (premium) discount on notes	24.3	(1.5)
Redeemable non-controlling interest expense	0.3	(3.3)
Distribution of earnings from unconsolidated affiliates	0.0	10.3
(Income) loss from unconsolidated affiliates	1.6	(9.7)
Changes in assets and liabilities net of assets acquired and liabilities assumed:
Accounts receivable, accrued revenue and other	(18.4)	57.3
Natural gas and NGLs inventory, prepaid expenses and other	12.1	(26.6)
Accounts payable, accrued gas and crude oil purchases and other accrued liabilities	2.9	(55.5)
Net cash provided by operating activities	304.2	277.0
Cash flows from investing activities, net of assets acquired and liabilities assumed:
Additions to property and equipment	(288.2)	(349.2)
Acquisition of business, net of cash acquired	(791.3)	(324.8)
Proceeds from sale of property	0.8	0.1
Investment in unconsolidated affiliates	(41.8)	0.0
Distribution from unconsolidated affiliates in excess of earnings	14.8	8.9
Net cash used in investing activities	(1,105.7)	(665.0)
Cash flows from financing activities:
Proceeds from borrowings	847.1	2,327.4
Payments on borrowings	(549.1)	(1,521.2)
Payments on capital lease obligations	(2.1)	(1.6)
Decrease in drafts payable	0.0	(12.4)
Debt financing costs	(0.4)	(9.5)
Mandatorily redeemable non-controlling interest	(4.0)	0.0
Conversion of restricted units, net of units withheld for taxes	(1.1)	(2.8)
Conversion of Partnership's restricted units, net of units withheld for taxes	(1.1)	(2.5)
Proceeds from issuance of Partnership's common units	52.3	4.1
Distributions to non-controlling partners	(186.6)	(175.7)
Distribution to Members	(92.7)	(79.3)
Contributions from Devon	1.4	28.8
Distributions to Devon for net assets acquired	0.0	(171.0)
Proceeds from issuance of Partnership Preferred Units	724.1	0.0
Contributions by non-controlling interest	5.9	7.3
Net cash provided by financing activities	793.7	391.6
Net increase (decrease) in cash and cash equivalents	(7.8)	3.6
Cash and cash equivalents, beginning of period	18.0	68.4
Cash and cash equivalents, end of period	10.2	72.0
Cash paid for interest	67.8	44.4
Cash paid (refund) for income taxes	$ (5.8)	$ 13.4