Consolidated Statement of Partners' Capital - USD ($) $ in Millions	Total	CMLP	Preferred Units	Common Unit Capital	Common Unit Capital CMLP	Limited Partners	Limited Partners CMLP	Non-Controlling Partner	Non-Controlling Partner CMLP	Total Partners’ Capital	Total Partners’ Capital CMLP	Subordinated units	Common units	Preferred Units
Balance at the beginning of the period at Dec. 31, 2016			$ 564.5			$ 1,782.0	$ 2,550.7	$ 192.5	$ 192.5	$ 2,539.0	$ 2,743.2
Balance at the beginning of the period (in units) at Dec. 31, 2016												400,000	69,100,000
Preferred units balance at the beginning of the period (in units) at Dec. 31, 2016														66,500,000
Increase (Decrease) in Partners' Capital [Roll Forward]
Proceeds from the issuance of common units				$ 15.2						15.2
Redemption of non-controlling interest								(202.7)	(202.7)	(202.7)	(202.7)
Issuance of common units (in units)	633,271												600,000
Unit-based compensation charges						25.5	25.5			25.5	25.5
Unit-based compensation charges (in units)													800,000
Taxes paid for unit-based compensation vesting						(5.5)	(5.5)			(5.5)	(5.5)
Taxes paid for unit-based compensation vesting (in units)													(200,000)
Distributions to partners			(15.0)			(167.6)	(174.0)	(15.2)	(15.2)	(197.8)	(189.2)
Issuance of non-controlling interest								175.0	175.0	175.0	175.0
Distributions to partners (in units)														4,800,000
Change in fair value of Suburban Propane Partners, L.P. units						(0.8)				(0.8)
Other				(0.9)	$ (0.5)			0.1	0.1	(0.8)	(0.4)
Net income (loss)	$ (166.6)	$ (175.5)	62.5			(254.4)	(200.8)	25.3	25.3	(166.6)	(175.5)
Balance at the beginning of the period (in units) at Dec. 31, 2017												400,000	70,300,000
Preferred units balance at the end of the period (in units) at Dec. 31, 2017														71,300,000
Balance at the end of the period at Dec. 31, 2017			612.0			1,393.5	2,195.4	175.0	175.0	2,180.5	2,370.4
Increase (Decrease) in Partners' Capital [Roll Forward]
Issuance of common units (in units)	0
Unit-based compensation charges						28.5	28.5	(9.9)		28.5	28.5
Unit-based compensation charges (in units)													1,100,000
Taxes paid for unit-based compensation vesting						(7.4)	(7.4)			(7.4)	(7.4)
Taxes paid for unit-based compensation vesting (in units)													(200,000)
Distributions to partners			(60.1)			(170.8)	(238.4)		(9.9)	(240.8)	(248.3)
Change in fair value of Suburban Propane Partners, L.P. units						(0.7)				(0.7)
Other				(0.8)	0.2					(0.8)	0.2
Net income (loss)	$ 67.0	58.6	60.1			(9.3)	42.4	16.2	16.2	67.0	58.6
Balance at the beginning of the period (in units) at Dec. 31, 2018												400,000	71,200,000
Preferred units balance at the end of the period (in units) at Dec. 31, 2018	71,257,445													71,300,000
Balance at the end of the period at Dec. 31, 2018	$ 1,852.5	2,028.2	612.0			1,240.5	2,028.2	181.3	181.3	2,033.8	2,209.5
Increase (Decrease) in Partners' Capital [Roll Forward]
Preferred units, issued	71,257,445
Issuance of common units (in units)	0
Unit-based compensation charges						42.4	42.4	(6.6)		42.4	42.4
Unit-based compensation charges (in units)													1,000,000.0
Taxes paid for unit-based compensation vesting						(11.0)	(11.0)			(11.0)	(11.0)
Taxes paid for unit-based compensation vesting (in units)													(300,000)
Distributions to partners			(60.1)			(172.4)	(235.8)		(6.6)	(239.1)	(242.4)
Change in fair value of Suburban Propane Partners, L.P. units						0.3				0.3
Non-controlling interest reclassification (Note 12)	$ 178.8							(178.8)	(178.8)	(178.8)	(178.8)
Other				(4.0)	(0.3)			0.1	0.1	(3.9)	(0.2)
Net income (loss)	$ 319.9	310.6	60.1			225.0	275.8	4.0	4.0	289.1	279.8
Balance at the beginning of the period (in units) at Dec. 31, 2019												400,000	71,900,000
Preferred units balance at the end of the period (in units) at Dec. 31, 2019	71,257,445													71,300,000
Balance at the end of the period at Dec. 31, 2019	$ 1,932.8	$ 2,099.3	$ 612.0			$ 1,320.8	$ 2,099.3	$ 0.0	$ 0.0	1,932.8	2,099.3
Increase (Decrease) in Partners' Capital [Roll Forward]
Preferred units, issued	71,257,445
Cumulative effect of accounting change (Note 2)				$ 7.5	$ 7.5					$ 7.5	$ 7.5