Schedule I - Crestwood Equity Partners LP - Parent Only - Condensed Statement of Cash Flows (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	$ 255.9	$ 346.1	$ 440.7
Cash flows from investing activities	38.7	867.2	(212.7)
Proceeds from the issuance of long-term debt	2,838.6	1,565.3	4,261.8
Payments on long-term debt	(2,913.9)	(2,536.3)	(4,113.0)
Payments for debt-related deferred costs	(1.0)	(3.5)	(17.3)
Distributions to partners	(167.6)	(219.8)	(171.5)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	(15.0)	0.0	0.0
Net cash provided by (used in) financing activities	(294.9)	(1,212.2)	(236.3)
Net change in cash	(0.3)	1.1	(8.3)
Cash at beginning of period	1.6	0.5	8.8
Cash at end of period	1.3	1.6	0.5
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash flows from operating activities	(3.6)	(3.5)	(14.7)
Cash flows from investing activities	174.0	227.6	593.8
Proceeds from the issuance of long-term debt	0.0	0.0	771.7
Payments on long-term debt	0.0	(0.2)	(1,152.1)
Distributions to partners	(182.6)	(219.8)	(171.5)
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	15.2	0.0	0.0
Change in intercompany balances	(3.0)	(4.2)	(30.5)
Net cash provided by (used in) financing activities	(170.4)	(224.2)	(582.4)
Net change in cash	0.0	(0.1)	(3.3)
Cash at beginning of period	0.3	0.4	3.7
Cash at end of period	$ 0.3	$ 0.3	$ 0.4