Segment Information - Reconciliation of Reportable Segment Operating Margin to Income (Loss) Before Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	$ 522.1	$ 479.5		$ 1,147.6	$ 1,145.5
Depreciation and amortization expense	(211.9)	(204.5)		(428.0)	(443.6)
General and administrative expense	(63.7)	(61.5)		(125.1)	(121.9)
Impairment of long-lived assets			$ (2,442.8)		(2,442.8)
Interest expense, net	(94.8)	(96.7)		(193.2)	(194.7)
Equity earnings (loss)	12.8	14.9		24.6	35.5
Gain (loss) on sale or disposition of business and assets	0.4	0.7		0.2
Write-down of assets	(1.1)			(4.7)
Gain (loss) from financing activities	(1.9)	21.8		(16.6)	61.1
Other, net	0.1	(0.3)		0.1	(0.8)
Income (loss) before income taxes	162.0	153.9		404.9	(1,961.7)
Gathering and Processing [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	301.2	237.2		576.6	492.8
Logistics And Transportation [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	291.4	231.5		640.1	525.5
Other [Member]
Reconciliation of reportable segment operating margin to income (loss) before income taxes:
Operating margin	$ (70.5)	$ 10.8		$ (69.1)	$ 127.2