Schedule I - Crestwood Equity Partners LP - Parent Only - Balance Sheet (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Condensed Financial Statements, Captions [Line Items]
Cash	$ 1.3	$ 1.6	$ 0.5	$ 8.8
Total current assets	530.5	373.4
Property, plant and equipment, net	1,820.8	2,097.6
Total assets	4,284.9	4,448.9
Accrued expenses	105.9	90.5
Current portion of long-term debt	0.9	1.0
Total current liabilities	505.1	337.3
Long-term debt, less current portion	1,491.3	1,522.7
Other long-term liabilities	104.7	44.6
Total partners’ capital	2,180.5	2,539.0	2,946.9	5,584.5
Total liabilities and partners’ capital	4,284.9	4,448.9
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash	0.3	0.3	$ 0.4	$ 3.7
Total current assets	0.3	0.3
Property, plant and equipment, net	1.2	1.4
Intangible assets, net	1.4	4.5
Investments in subsidiaries	2,005.1	2,342.7
Other assets	3.5	4.3
Total assets	2,011.5	2,353.2
Accounts payable	2.7	2.7
Accrued expenses	1.2	1.4
Total current liabilities	3.9	4.1
Other long-term liabilities	2.1	2.6
Total partners’ capital	2,005.5	2,346.5
Total liabilities and partners’ capital	$ 2,011.5	$ 2,353.2