Schedule I - Crestwood Equity Partners LP - Parent Only - Statement of Operations (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Revenues		$ 2,520.5	$ 2,632.8	$ 3,931.3
Operating income (loss)		(108.7)	(2,084.8)	117.9
Interest and debt expense, net		(125.1)	(140.1)	(127.1)
Gain (loss) on modification/extinguishment of debt	$ 10.0	10.0	(20.0)	0.0
Other income, net		0.5	0.6	0.6
Loss before income taxes		(191.8)	(2,305.1)	(9.3)
(Provision) benefit for income taxes		(0.3)	1.4	(1.1)
Net loss		(192.1)	(2,303.7)	(10.4)
Net income attributable to non-controlling partners in subsidiary		24.2	(636.8)	(66.8)
Net income (loss) attributable to parent		(216.3)	(1,666.9)	56.4
Parent Company
Condensed Financial Statements, Captions [Line Items]
Revenues		0.0	0.0	0.0
Costs and Expenses		6.0	14.5	8.5
Operating income (loss)		(6.0)	(14.5)	(8.5)
Interest and debt expense, net		0.0	(9.6)	(15.7)
Loss from unconsolidated affiliates		(186.6)	(2,279.1)	14.2
Gain (loss) on modification/extinguishment of debt		0.0	(1.1)	0.0
Other income, net		0.5	0.6	0.0
Loss before income taxes		(192.1)	(2,303.7)	(10.0)
(Provision) benefit for income taxes		0.0	0.0	(0.4)
Net loss		(192.1)	(2,303.7)	(10.4)
Net income attributable to non-controlling partners in subsidiary		24.2	(636.8)	(66.8)
Net income (loss) attributable to parent		$ (216.3)	$ (1,666.9)	$ 56.4