Consolidated Statement of Partners' Capital - USD ($) $ in Millions	Total	Preferred Units	Common unit	Partners' Capital	Crestwood Midstream Partners LP	Crestwood Midstream Partners LP Partners' Capital	Preferred Units	Common Units	Subordinated Units
Preferred units, beginning balance (in units) at Dec. 31, 2019							71,300,000
Partner units, beginning balance (in units) at Dec. 31, 2019								71,900,000	400,000
Beginning balance at Dec. 31, 2019		$ 612.0	$ 1,320.8	$ 1,932.8		$ 2,099.3
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(45.3)	(60.3)		(57.0)
Unit-based compensation charges (in shares)								1,700,000
Unit-based compensation charges			0.2	0.2		(4.4)
Taxes paid for unit-based compensation vesting (in shares)								(500,000)
Taxes paid for unit-based compensation vesting			(15.1)	(15.1)		(15.1)
Change in fair value of Suburban Propane Partners, L.P. units			(1.1)	(1.1)
Other			3.5	3.5		(1.1)
Net income (loss) attributable to parent		15.0	(48.3)	(33.3)		(35.5)
Preferred units, ending balance (in units) at Mar. 31, 2020							71,300,000
Partner units, ending balance (in units) at Mar. 31, 2020								73,300,000	400,000
Ending Balance at Mar. 31, 2020		612.0	1,214.7	1,826.7		1,986.2
Preferred units, beginning balance (in units) at Dec. 31, 2019							71,300,000
Partner units, beginning balance (in units) at Dec. 31, 2019								71,900,000	400,000
Beginning balance at Dec. 31, 2019		612.0	1,320.8	1,932.8		2,099.3
Increase (Decrease) in Partners' Capital [Roll Forward]
Change in fair value of Suburban Propane Partners, L.P. units	$ (0.8)
Net income (loss) attributable to parent	(73.5)				$ (80.5)
Preferred units, ending balance (in units) at Sep. 30, 2020							71,300,000
Partner units, ending balance (in units) at Sep. 30, 2020								73,600,000	400,000
Ending Balance at Sep. 30, 2020		612.0	1,073.2	1,685.2		1,837.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Other (in shares)								200,000
Preferred units, beginning balance (in units) at Mar. 31, 2020							71,300,000
Partner units, beginning balance (in units) at Mar. 31, 2020								73,300,000	400,000
Beginning balance at Mar. 31, 2020		612.0	1,214.7	1,826.7		1,986.2
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(45.7)	(60.7)		(62.0)
Unit-based compensation charges			13.6	13.6		13.6
Taxes paid for unit-based compensation vesting (in shares)								(100,000)
Taxes paid for unit-based compensation vesting			(0.4)	(0.4)		(0.4)
Other			(0.1)	(0.1)		0.1
Net income (loss) attributable to parent		15.0	(49.5)	(34.5)		(37.0)
Preferred units, ending balance (in units) at Jun. 30, 2020							71,300,000
Partner units, ending balance (in units) at Jun. 30, 2020								73,200,000	400,000
Ending Balance at Jun. 30, 2020		612.0	1,132.6	1,744.6		1,900.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(45.7)	(60.7)		(61.9)
Unit-based compensation charges (in shares)								400,000
Unit-based compensation charges			7.1	7.1		7.1
Taxes paid for unit-based compensation vesting			(0.1)	(0.1)		(0.1)
Change in fair value of Suburban Propane Partners, L.P. units	0.3		0.3	0.3
Other			(0.3)	(0.3)		(0.1)
Net income (loss) attributable to parent	$ (5.7)	15.0	(20.7)	(5.7)	(8.0)	(8.0)
Preferred units, ending balance (in units) at Sep. 30, 2020							71,300,000
Partner units, ending balance (in units) at Sep. 30, 2020								73,600,000	400,000
Ending Balance at Sep. 30, 2020		612.0	1,073.2	1,685.2		1,837.5
Preferred units, beginning balance (in units) at Dec. 31, 2020	71,257,445						71,300,000
Partner units, beginning balance (in units) at Dec. 31, 2020								73,600,000	400,000
Beginning balance at Dec. 31, 2020		612.0	1,043.4	1,655.4	1,805.1	1,805.1
Increase (Decrease) in Partners' Capital [Roll Forward]
Stock Repurchased and Retired During Period, Value			(273.2)	(273.2)
Treasury Stock, Shares, Retired								(11,500,000)	(400,000)
Distributions to partners		(15.0)	(46.4)	(61.4)		(334.0)
Unit-based compensation charges (in shares)								1,100,000
Unit-based compensation charges			3.7	3.7		2.3
Taxes paid for unit-based compensation vesting (in shares)								(400,000)
Taxes paid for unit-based compensation vesting			(8.1)	(8.1)		(8.1)
Other			(0.4)	(0.4)		(0.1)
Net income (loss) attributable to parent		15.0	(63.4)	(48.4)		(50.5)
Preferred units, ending balance (in units) at Mar. 31, 2021							71,300,000
Partner units, ending balance (in units) at Mar. 31, 2021								62,800,000	0
Ending Balance at Mar. 31, 2021		612.0	655.6	1,267.6		1,414.7
Preferred units, beginning balance (in units) at Dec. 31, 2020	71,257,445						71,300,000
Partner units, beginning balance (in units) at Dec. 31, 2020								73,600,000	400,000
Beginning balance at Dec. 31, 2020		612.0	1,043.4	1,655.4	1,805.1	1,805.1
Increase (Decrease) in Partners' Capital [Roll Forward]
Change in fair value of Suburban Propane Partners, L.P. units	$ 0.0
Net income (loss) attributable to parent	$ (146.7)				(151.4)
Preferred units, ending balance (in units) at Sep. 30, 2021	71,257,445						71,300,000
Partner units, ending balance (in units) at Sep. 30, 2021								62,900,000	0
Ending Balance at Sep. 30, 2021		612.0	464.3	1,076.3	1,213.5	1,213.5
Preferred units, beginning balance (in units) at Mar. 31, 2021							71,300,000
Partner units, beginning balance (in units) at Mar. 31, 2021								62,800,000	0
Beginning balance at Mar. 31, 2021		612.0	655.6	1,267.6		1,414.7
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(39.3)	(54.3)		(61.4)
Unit-based compensation charges (in shares)								0
Unit-based compensation charges			7.6	7.6		7.6
Taxes paid for unit-based compensation vesting (in shares)								0
Taxes paid for unit-based compensation vesting			(0.1)	(0.1)		(0.1)
Other			(0.3)	(0.3)
Net income (loss) attributable to parent		15.0	(63.4)	(48.4)		(48.8)
Preferred units, ending balance (in units) at Jun. 30, 2021							71,300,000
Partner units, ending balance (in units) at Jun. 30, 2021								62,800,000	0
Ending Balance at Jun. 30, 2021		612.0	560.1	1,172.1		1,312.0
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(39.3)	(54.3)		(55.9)
Unit-based compensation charges (in shares)								100,000
Unit-based compensation charges			9.6	9.6		9.6
Taxes paid for unit-based compensation vesting (in shares)								0
Taxes paid for unit-based compensation vesting			(0.1)	(0.1)		(0.1)
Change in fair value of Suburban Propane Partners, L.P. units	$ 0.0
Other			(1.1)	(1.1)
Net income (loss) attributable to parent	$ (49.9)	15.0	(64.9)	(49.9)	(52.1)	(52.1)
Preferred units, ending balance (in units) at Sep. 30, 2021	71,257,445						71,300,000
Partner units, ending balance (in units) at Sep. 30, 2021								62,900,000	0
Ending Balance at Sep. 30, 2021		$ 612.0	$ 464.3	$ 1,076.3	$ 1,213.5	$ 1,213.5