Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current assets:
Cash	$ 1.3	$ 1.6	$ 0.5	$ 8.8
Accounts receivable	442.7	289.8
Inventory	68.4	66.0
Total current assets	530.5	373.4
Property, plant and equipment, net	1,820.8	2,097.6
Investments in unconsolidated affiliates	1,183.0	1,115.4
Other assets	5.8	6.1
Total assets	4,284.9	4,448.9
Current liabilities:
Accounts payable	349.4	217.2
Total current liabilities	505.1	337.3
Long-term liabilities:
Long-term debt, less current portion	1,491.3	1,522.7
Other long-term liabilities	104.7	44.6
Deferred income taxes	3.3	5.3
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
Eliminations
Current assets:
Cash	0.0	0.0	0.0	0.0
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	0.0	0.0
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investments in consolidated affiliates	(3,705.4)	(4,093.7)
Investments in unconsolidated affiliates	0.0	0.0
Other assets	0.0	0.0
Total assets	(3,705.4)	(4,093.7)
Current liabilities:
Accounts payable	0.0	0.0
Total current liabilities	0.0	0.0
Total current liabilities	0.0	0.0
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	(3,705.4)	(4,093.7)
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	(3,705.4)	(4,093.7)
Total liabilities and partners’ capital	(3,705.4)	(4,093.7)
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Current assets:
Cash	1.0	1.3	0.1	0.0
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	1.0	1.3
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investments in consolidated affiliates	3,705.4	4,093.7
Investments in unconsolidated affiliates	0.0	0.0
Other assets	0.0	0.0
Total assets	3,706.4	4,095.0
Current liabilities:
Accounts payable	0.0	0.0
Total current liabilities	20.5	23.1
Total current liabilities	20.5	23.1
Long-term liabilities:
Long-term debt, less current portion	1,490.5	1,521.2
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	2,195.4	2,550.7
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	2,195.4	2,550.7
Total liabilities and partners’ capital	3,706.4	4,095.0
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0	0.0	7.6
Accounts receivable	439.7	289.3
Inventory	68.4	66.0
Other	18.1	16.0
Total current assets	526.2	371.3
Property, plant and equipment, net	2,007.5	2,298.4
Intangible Assets, Net (Including Goodwill)	743.3	851.9
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	0.0	0.0
Other assets	2.4	1.8
Total assets	3,279.4	3,523.4
Current liabilities:
Accounts payable	346.8	214.5
Total current liabilities	134.0	94.4
Total current liabilities	480.8	308.9
Long-term liabilities:
Long-term debt, less current portion	0.8	1.5
Other long-term liabilities	45.6	42.0
Deferred income taxes	0.7	0.7
Partners' capital	2,751.5	3,170.3
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	2,751.5	3,170.3
Total liabilities and partners’ capital	3,279.4	3,523.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0	0.0	0.0
Accounts receivable	2.9	0.5
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	2.9	0.5
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	1,183.0	1,115.4
Other assets	0.0	0.0
Total assets	1,185.9	1,115.9
Current liabilities:
Accounts payable	0.0	0.0
Total current liabilities	0.0	0.0
Total current liabilities	0.0	0.0
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	57.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	953.9	923.4
Interest of non-controlling partners in subsidiary	175.0	192.5
Total partners’ capital	1,128.9	1,115.9
Total liabilities and partners’ capital	1,185.9	1,115.9
CMLP
Current assets:
Cash	1.0	1.3	$ 0.1	$ 7.6
Accounts receivable	442.6	289.8
Inventory	68.4	66.0
Other	18.1	16.0
Total current assets	530.1	373.1
Property, plant and equipment, net	2,007.5	2,298.4
Intangible Assets, Net (Including Goodwill)	743.3	851.9
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	1,183.0	1,115.4
Other assets	2.4	1.8
Total assets	4,466.3	4,640.6
Current liabilities:
Accounts payable	346.8	214.5
Total current liabilities	154.5	117.5
Total current liabilities	501.3	332.0
Long-term liabilities:
Long-term debt, less current portion	1,491.3	1,522.7
Other long-term liabilities	102.6	42.0
Deferred income taxes	0.7	0.7
Partners' capital	2,195.4	2,550.7
Interest of non-controlling partners in subsidiary	175.0	192.5
Total partners’ capital	2,370.4	2,743.2
Total liabilities and partners’ capital	$ 4,466.3	$ 4,640.6