Segment Information - Financial Information and Assets (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Segment Reporting
Revenue from contracts with customers	$ 933.6	$ 1,400.5	$ 2,837.8	$ 4,881.0
Cost of sales	(549.5)	(999.5)	(1,702.5)	(3,663.0)
Operating expenses	(94.3)	(119.2)	(283.1)	(351.6)
Gain (loss) on derivative activity	(5.1)	7.5	(8.3)	16.2
Segment profit (loss)	284.7	289.3	843.9	882.6
Depreciation and amortization	(160.3)	(157.3)	(481.3)	(463.1)
Impairments	0.0	0.0	(354.5)	(186.5)
Goodwill	0.0	1,123.7	0.0	1,123.7	$ 184.6
Capital expenditures	43.2	196.5	227.2	619.1
Permian
Segment Reporting
Revenue from contracts with customers	254.7	539.4	831.0	2,024.3
Cost of sales	(185.4)	(474.2)	(637.7)	(1,830.9)
Operating expenses	(22.9)	(28.9)	(71.1)	(85.1)
Gain (loss) on derivative activity	0.0	0.0	0.0	0.0
Segment profit (loss)	46.4	36.3	122.2	108.3
Depreciation and amortization	(31.9)	(31.6)	(92.1)	(89.6)
Impairments			(184.6)	0.0
Goodwill		184.6		184.6
Capital expenditures	28.5	119.7	161.4	268.0
Louisiana
Segment Reporting
Revenue from contracts with customers	541.5	635.0	1,514.7	2,163.6
Cost of sales	(441.4)	(529.6)	(1,213.6)	(1,844.1)
Operating expenses	(31.1)	(38.4)	(90.4)	(111.6)
Gain (loss) on derivative activity	0.0	0.0	0.0	0.0
Segment profit (loss)	69.0	67.0	210.7	207.9
Depreciation and amortization	(36.9)	(37.3)	(109.3)	(116.0)
Impairments			(169.9)	(186.5)
Goodwill		0.0		0.0
Capital expenditures	8.5	21.5	39.3	82.0
Oklahoma
Segment Reporting
Revenue from contracts with customers	228.9	283.2	628.7	902.1
Cost of sales	(101.0)	(148.4)	(255.8)	(492.0)
Operating expenses	(20.1)	(25.7)	(62.4)	(77.2)
Gain (loss) on derivative activity	0.0	0.0	0.0	0.0
Segment profit (loss)	107.8	109.1	310.5	332.9
Depreciation and amortization	(53.0)	(51.1)	(163.7)	(144.8)
Impairments			0.0	0.0
Goodwill		813.4		813.4
Capital expenditures	2.6	48.6	14.1	227.1
North Texas
Segment Reporting
Revenue from contracts with customers	115.0	137.0	342.1	461.1
Cost of sales	(28.2)	(41.4)	(74.1)	(166.1)
Operating expenses	(20.2)	(26.2)	(59.2)	(77.7)
Gain (loss) on derivative activity	0.0	0.0	0.0	0.0
Segment profit (loss)	66.6	69.4	208.8	217.3
Depreciation and amortization	(36.8)	(35.4)	(110.4)	(106.6)
Impairments			0.0	0.0
Goodwill		125.7		125.7
Capital expenditures	3.0	5.0	10.7	36.3
Corporate
Segment Reporting
Revenue from contracts with customers	(206.5)	(194.1)	(478.7)	(670.1)
Cost of sales	206.5	194.1	478.7	670.1
Operating expenses	0.0	0.0	0.0	0.0
Gain (loss) on derivative activity	(5.1)	7.5	(8.3)	16.2
Segment profit (loss)	(5.1)	7.5	(8.3)	16.2
Depreciation and amortization	(1.7)	(1.9)	(5.8)	(6.1)
Impairments			0.0	0.0
Goodwill		0.0		0.0
Capital expenditures	0.6	1.7	1.7	5.7
Product sales
Segment Reporting
Revenue from contracts with customers	696.1	1,137.2	2,121.6	4,118.5
Product sales | Permian
Segment Reporting
Revenue from contracts with customers	129.2	434.0	548.8	1,682.5
Product sales | Louisiana
Segment Reporting
Revenue from contracts with customers	500.4	587.6	1,378.5	2,026.6
Product sales | Oklahoma
Segment Reporting
Revenue from contracts with customers	50.5	87.4	143.3	280.7
Product sales | North Texas
Segment Reporting
Revenue from contracts with customers	16.0	28.2	51.0	128.7
Product sales | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, Natural gas sales
Segment Reporting
Revenue from contracts with customers	179.0	193.1	481.3	657.4
Product sales, Natural gas sales | Permian
Segment Reporting
Revenue from contracts with customers	46.5	24.3	94.0	59.4
Product sales, Natural gas sales | Louisiana
Segment Reporting
Revenue from contracts with customers	76.4	92.0	226.6	316.8
Product sales, Natural gas sales | Oklahoma
Segment Reporting
Revenue from contracts with customers	40.1	54.6	110.0	176.5
Product sales, Natural gas sales | North Texas
Segment Reporting
Revenue from contracts with customers	16.0	22.2	50.7	104.7
Product sales, Natural gas sales | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, NGL sales
Segment Reporting
Revenue from contracts with customers	403.6	431.9	1,060.3	1,535.6
Product sales, NGL sales | Permian
Segment Reporting
Revenue from contracts with customers	0.1	0.3	0.2	0.9
Product sales, NGL sales | Louisiana
Segment Reporting
Revenue from contracts with customers	402.3	421.0	1,056.9	1,492.9
Product sales, NGL sales | Oklahoma
Segment Reporting
Revenue from contracts with customers	1.2	4.6	2.9	17.8
Product sales, NGL sales | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	6.0	0.3	24.0
Product sales, NGL sales | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, Crude oil and condensate sales
Segment Reporting
Revenue from contracts with customers	113.5	512.2	580.0	1,925.5
Product sales, Crude oil and condensate sales | Permian
Segment Reporting
Revenue from contracts with customers	82.6	409.4	454.6	1,622.2
Product sales, Crude oil and condensate sales | Louisiana
Segment Reporting
Revenue from contracts with customers	21.7	74.6	95.0	216.9
Product sales, Crude oil and condensate sales | Oklahoma
Segment Reporting
Revenue from contracts with customers	9.2	28.2	30.4	86.4
Product sales, Crude oil and condensate sales | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, Crude oil and condensate sales | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales—related parties
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales—related parties | Permian
Segment Reporting
Revenue from contracts with customers	95.6	72.0	201.1	256.9
Product sales—related parties | Louisiana
Segment Reporting
Revenue from contracts with customers	3.3	9.6	13.3	18.1
Product sales—related parties | Oklahoma
Segment Reporting
Revenue from contracts with customers	85.4	90.2	208.9	320.9
Product sales—related parties | North Texas
Segment Reporting
Revenue from contracts with customers	22.1	22.1	55.1	75.8
Product sales—related parties | Corporate
Segment Reporting
Revenue from contracts with customers	(206.4)	(193.9)	(478.4)	(671.7)
Product sales, Natural gas sales—related parties
Segment Reporting
Revenue from contracts with customers		0.0		0.0
Product sales, Natural gas sales—related parties | Permian
Segment Reporting
Revenue from contracts with customers		(0.1)		0.3
Product sales, Natural gas sales—related parties | Louisiana
Segment Reporting
Revenue from contracts with customers		0.0		0.0
Product sales, Natural gas sales—related parties | Oklahoma
Segment Reporting
Revenue from contracts with customers		0.0		0.0
Product sales, Natural gas sales—related parties | North Texas
Segment Reporting
Revenue from contracts with customers		0.0		0.3
Product sales, Natural gas sales—related parties | Corporate
Segment Reporting
Revenue from contracts with customers		0.1		(0.6)
Product sales, NGL sales, related party
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, NGL sales, related party | Permian
Segment Reporting
Revenue from contracts with customers	95.6	69.3	201.0	242.9
Product sales, NGL sales, related party | Louisiana
Segment Reporting
Revenue from contracts with customers	3.3	7.9	13.3	16.4
Product sales, NGL sales, related party | Oklahoma
Segment Reporting
Revenue from contracts with customers	85.4	90.2	209.0	320.9
Product sales, NGL sales, related party | North Texas
Segment Reporting
Revenue from contracts with customers	21.4	21.0	52.5	71.7
Product sales, NGL sales, related party | Corporate
Segment Reporting
Revenue from contracts with customers	(205.7)	(188.4)	(475.8)	(651.9)
Product sales, Crude oil and condensate sales, related party
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Product sales, Crude oil and condensate sales, related party | Permian
Segment Reporting
Revenue from contracts with customers	0.0	2.8	0.1	13.7
Product sales, Crude oil and condensate sales, related party | Louisiana
Segment Reporting
Revenue from contracts with customers	0.0	1.7	0.0	1.7
Product sales, Crude oil and condensate sales, related party | Oklahoma
Segment Reporting
Revenue from contracts with customers	0.0	0.0	(0.1)	0.0
Product sales, Crude oil and condensate sales, related party | North Texas
Segment Reporting
Revenue from contracts with customers	0.7	1.1	2.6	3.8
Product sales, Crude oil and condensate sales, related party | Corporate
Segment Reporting
Revenue from contracts with customers	(0.7)	(5.6)	(2.6)	(19.2)
Midstream services
Segment Reporting
Revenue from contracts with customers	237.5	263.3	716.2	762.5
Midstream services | Permian
Segment Reporting
Revenue from contracts with customers	29.9	33.4	81.1	84.9
Midstream services | Louisiana
Segment Reporting
Revenue from contracts with customers	37.8	37.8	122.9	122.2
Midstream services | Oklahoma
Segment Reporting
Revenue from contracts with customers	92.9	105.4	276.2	298.8
Midstream services | North Texas
Segment Reporting
Revenue from contracts with customers	76.9	86.7	236.0	256.6
Midstream services | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Gathering and transportation
Segment Reporting
Revenue from contracts with customers	128.7	140.7	380.2	409.6
Midstream services, Gathering and transportation | Permian
Segment Reporting
Revenue from contracts with customers	17.9	14.7	47.3	36.3
Midstream services, Gathering and transportation | Louisiana
Segment Reporting
Revenue from contracts with customers	10.7	12.2	33.9	46.1
Midstream services, Gathering and transportation | Oklahoma
Segment Reporting
Revenue from contracts with customers	56.7	63.7	165.5	178.2
Midstream services, Gathering and transportation | North Texas
Segment Reporting
Revenue from contracts with customers	43.4	50.1	133.5	149.0
Midstream services, Gathering and transportation | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Processing
Segment Reporting
Revenue from contracts with customers	74.0	81.1	220.9	238.1
Midstream services, Processing | Permian
Segment Reporting
Revenue from contracts with customers	8.0	8.3	19.8	23.3
Midstream services, Processing | Louisiana
Segment Reporting
Revenue from contracts with customers	0.3	0.8	1.6	2.5
Midstream services, Processing | Oklahoma
Segment Reporting
Revenue from contracts with customers	32.4	35.7	97.8	105.5
Midstream services, Processing | North Texas
Segment Reporting
Revenue from contracts with customers	33.3	36.3	101.7	106.8
Midstream services, Processing | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, NGL services
Segment Reporting
Revenue from contracts with customers	14.2	11.2	52.5	32.9
Midstream services, NGL services | Permian
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, NGL services | Louisiana
Segment Reporting
Revenue from contracts with customers	14.2	11.2	52.4	32.9
Midstream services, NGL services | Oklahoma
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, NGL services | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.1	0.0
Midstream services, NGL services | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services
Segment Reporting
Revenue from contracts with customers	19.7	25.8	59.4	72.2
Midstream services, Crude services | Permian
Segment Reporting
Revenue from contracts with customers	3.8	6.4	13.0	16.9
Midstream services, Crude services | Louisiana
Segment Reporting
Revenue from contracts with customers	12.2	13.5	33.8	40.2
Midstream services, Crude services | Oklahoma
Segment Reporting
Revenue from contracts with customers	3.7	5.9	12.6	15.1
Midstream services, Crude services | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Other services
Segment Reporting
Revenue from contracts with customers	0.9	4.5	3.2	9.7
Midstream services, Other services | Permian
Segment Reporting
Revenue from contracts with customers	0.2	4.0	1.0	8.4
Midstream services, Other services | Louisiana
Segment Reporting
Revenue from contracts with customers	0.4	0.1	1.2	0.5
Midstream services, Other services | Oklahoma
Segment Reporting
Revenue from contracts with customers	0.1	0.1	0.3	0.0
Midstream services, Other services | North Texas
Segment Reporting
Revenue from contracts with customers	0.2	0.3	0.7	0.8
Midstream services, Other services | Corporate
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services—related parties
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services—related parties | Permian
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services—related parties | Louisiana
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	(3.3)
Midstream services—related parties | Oklahoma
Segment Reporting
Revenue from contracts with customers	0.1	0.2	0.3	1.7
Midstream services—related parties | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services—related parties | Corporate
Segment Reporting
Revenue from contracts with customers	(0.1)	(0.2)	(0.3)	1.6
Midstream services, NGL services, related party
Segment Reporting
Revenue from contracts with customers				0.0
Midstream services, NGL services, related party | Permian
Segment Reporting
Revenue from contracts with customers				0.0
Midstream services, NGL services, related party | Louisiana
Segment Reporting
Revenue from contracts with customers				(3.3)
Midstream services, NGL services, related party | Oklahoma
Segment Reporting
Revenue from contracts with customers				0.0
Midstream services, NGL services, related party | North Texas
Segment Reporting
Revenue from contracts with customers				0.0
Midstream services, NGL services, related party | Corporate
Segment Reporting
Revenue from contracts with customers				3.3
Midstream services, Crude services, related party
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services, related party | Permian
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services, related party | Louisiana
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services, related party | Oklahoma
Segment Reporting
Revenue from contracts with customers	0.1	0.2	0.3	1.7
Midstream services, Crude services, related party | North Texas
Segment Reporting
Revenue from contracts with customers	0.0	0.0	0.0	0.0
Midstream services, Crude services, related party | Corporate
Segment Reporting
Revenue from contracts with customers	$ (0.1)	$ (0.2)	$ (0.3)	$ (1.7)