Consolidated Statement of Partners' Capital - USD ($) $ in Millions	Total	Preferred Units	Common unit	Non-Controlling Partners	Partners' Capital	Crestwood Midstream Partners LP	Crestwood Midstream Partners LP Common unit	Crestwood Midstream Partners LP Non-Controlling Partners	Crestwood Midstream Partners LP Partners' Capital	Preferred Units	Common Units	Subordinated Units
Partner units, beginning balance (in units) at Dec. 31, 2018											71,200,000	400,000
Preferred units, beginning balance (in units) at Dec. 31, 2018										71,300,000
Beginning balance at Dec. 31, 2018		$ 612.0	$ 1,240.5	$ 181.3	$ 2,033.8		$ 2,028.2	$ 181.3	$ 2,209.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(43.1)	(3.3)	(61.4)		(57.8)	(3.3)	(61.1)
Unit-based compensation charges			17.3		17.3		17.3		17.3
Unit-based compensation charges (in shares)											900,000
Taxes paid for unit-based compensation vesting			(7.0)		(7.0)		(7.0)		(7.0)
Taxes paid for unit-based compensation vesting (in shares)											(200,000)
Change in fair value of Suburban Propane Partners, L.P. units			0.4		0.4
Other			(0.7)		(0.7)		(0.3)		(0.3)
Net income (loss)		15.0	(4.9)	4.0	14.1		7.6	4.0	11.6
Preferred units, ending balance (in units) at Mar. 31, 2019										71,300,000
Partner units, ending balance (in units) at Mar. 31, 2019											71,900,000	400,000
Ending Balance at Mar. 31, 2019		612.0	1,202.5	182.0	1,996.5		1,988.0	182.0	2,170.0
Partner units, beginning balance (in units) at Dec. 31, 2018											71,200,000	400,000
Preferred units, beginning balance (in units) at Dec. 31, 2018										71,300,000
Beginning balance at Dec. 31, 2018		612.0	1,240.5	181.3	2,033.8		2,028.2	181.3	2,209.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Non-controlling interest reclassification (Note 10)	$ 178.8
Change in fair value of Suburban Propane Partners, L.P. units	0.6
Net income (loss)	272.7					$ 265.7
Preferred units, ending balance (in units) at Sep. 30, 2019										71,300,000
Partner units, ending balance (in units) at Sep. 30, 2019											71,800,000	400,000
Ending Balance at Sep. 30, 2019		612.0	1,340.6	0.0	1,952.6		2,118.8	0.0	2,118.8
Partner units, beginning balance (in units) at Mar. 31, 2019											71,900,000	400,000
Preferred units, beginning balance (in units) at Mar. 31, 2019										71,300,000
Beginning balance at Mar. 31, 2019		612.0	1,202.5	182.0	1,996.5		1,988.0	182.0	2,170.0
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(43.1)	(3.3)	(61.4)		(59.7)	(3.3)	(63.0)
Unit-based compensation charges			11.3		11.3		11.3		11.3
Taxes paid for unit-based compensation vesting			(3.6)		(3.6)		(3.6)		(3.6)
Non-controlling interest reclassification (Note 10)				(178.8)	(178.8)			(178.8)	(178.8)
Taxes paid for unit-based compensation vesting (in shares)											(100,000)
Change in fair value of Suburban Propane Partners, L.P. units			0.3		0.3
Other			(0.4)	0.1	(0.3)		(0.1)	0.1	0.0
Net income (loss)		15.0	199.4	0.0	214.4		212.3		212.3
Preferred units, ending balance (in units) at Jun. 30, 2019										71,300,000
Partner units, ending balance (in units) at Jun. 30, 2019											71,800,000	400,000
Ending Balance at Jun. 30, 2019		612.0	1,366.4	0.0	1,978.4		2,148.2	0.0	2,148.2
Increase (Decrease) in Partners' Capital [Roll Forward]
Distributions to partners		(15.0)	(43.1)	0.0	(58.1)		(59.8)		(59.8)
Unit-based compensation charges			9.3		9.3		9.3		9.3
Taxes paid for unit-based compensation vesting			(0.3)		(0.3)		(0.3)		(0.3)
Taxes paid for unit-based compensation vesting (in shares)											0
Change in fair value of Suburban Propane Partners, L.P. units	(0.1)		(0.1)		(0.1)
Other			(0.3)	0.0	(0.3)		0.1		0.1
Net income (loss)	$ 33.6	15.0	8.7	0.0	23.7	31.2	21.3		21.3
Preferred units, ending balance (in units) at Sep. 30, 2019										71,300,000
Partner units, ending balance (in units) at Sep. 30, 2019											71,800,000	400,000
Ending Balance at Sep. 30, 2019		612.0	1,340.6	$ 0.0	1,952.6		$ 2,118.8	$ 0.0	2,118.8
Partner units, beginning balance (in units) at Dec. 31, 2019											71,900,000	400,000
Preferred units, beginning balance (in units) at Dec. 31, 2019	71,257,445									71,300,000
Beginning balance at Dec. 31, 2019		612.0	1,320.8		1,932.8	2,099.3			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			0.2		0.2				(4.4)
Unit-based compensation charges (in shares)											1,700,000
Taxes paid for unit-based compensation vesting			(15.1)		(15.1)				(15.1)
Taxes paid for unit-based compensation vesting (in shares)											(500,000)
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)		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
Partner units, beginning balance (in units) at Dec. 31, 2019											71,900,000	400,000
Preferred units, beginning balance (in units) at Dec. 31, 2019	71,257,445									71,300,000
Beginning balance at Dec. 31, 2019		612.0	1,320.8		1,932.8	2,099.3			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)	$ (43.1)					(50.1)
Preferred units, ending balance (in units) at Sep. 30, 2020	71,257,445									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			1,837.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Other (in shares)											200,000
Partner units, beginning balance (in units) at Mar. 31, 2020											73,300,000	400,000
Preferred units, beginning balance (in units) at Mar. 31, 2020										71,300,000
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
Unit-based compensation charges (in shares)											0
Taxes paid for unit-based compensation vesting			(0.4)		(0.4)				(0.4)
Taxes paid for unit-based compensation vesting (in shares)											(100,000)
Other			(0.1)		(0.1)				0.1
Net income (loss)		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]
Other (in shares)											0
Distributions to partners		(15.0)	(45.7)		(60.7)				(61.9)
Unit-based compensation charges			7.1		7.1				7.1
Unit-based compensation charges (in shares)											400,000
Taxes paid for unit-based compensation vesting			(0.1)		(0.1)				(0.1)
Taxes paid for unit-based compensation vesting (in shares)											0
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)	$ 4.6	15.0	(20.7)		(5.7)	2.3			(8.0)
Preferred units, ending balance (in units) at Sep. 30, 2020	71,257,445									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			$ 1,837.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Other (in shares)											0