Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Current assets:
Cash	$ 1.4	$ 1.6	$ 1.0	$ 0.5
Accounts receivable	345.0	289.8
Inventory	92.9	66.0
Total current assets	452.3	373.4
Property, plant and equipment, net	2,052.1	2,097.6
Investment	1,198.5	1,115.4
Other assets	6.2	6.1
Total assets	4,525.3	4,448.9
Current liabilities:
Accounts payable	312.7	217.2
Total current liabilities	478.7	337.3
Long-term liabilities:
Long-term debt, less current portion	1,615.4	1,522.7
Other long-term liabilities	48.2	44.6
Deferred income taxes	4.7	5.3
Total partners’ capital	2,378.3	2,539.0
Total liabilities and partners’ capital	4,525.3	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
Investment in consolidated affiliates	(4,025.8)	(4,093.7)
Investment	0.0	0.0
Other assets	0.0	0.0
Total assets	(4,025.8)	(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	(4,025.8)	(4,093.7)
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	(4,025.8)	(4,093.7)
Total liabilities and partners’ capital	(4,025.8)	(4,093.7)
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Current assets:
Cash	1.1	1.3	0.5	0.1
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	1.1	1.3
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investment in consolidated affiliates	4,025.8	4,093.7
Investment	0.0	0.0
Other assets	0.0	0.0
Total assets	4,026.9	4,095.0
Current liabilities:
Accounts payable	0.0	0.0
Total current liabilities	39.9	23.1
Total current liabilities	39.9	23.1
Long-term liabilities:
Long-term debt, less current portion	1,614.6	1,521.2
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	2,372.4	2,550.7
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	2,372.4	2,550.7
Total liabilities and partners’ capital	4,026.9	4,095.0
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0	0.0	0.0
Accounts receivable	341.0	289.3
Inventory	92.9	66.0
Other	13.0	16.0
Total current assets	446.9	371.3
Property, plant and equipment, net	2,242.2	2,298.4
Intangible Assets, Net (Including Goodwill)	814.0	851.9
Investment in consolidated affiliates	0.0	0.0
Investment	0.0	0.0
Other assets	2.6	1.8
Total assets	3,505.7	3,523.4
Current liabilities:
Accounts payable	310.0	214.5
Total current liabilities	125.4	94.4
Total current liabilities	435.4	308.9
Long-term liabilities:
Long-term debt, less current portion	0.8	1.5
Other long-term liabilities	45.3	42.0
Deferred income taxes	0.7	0.7
Partners' capital	3,023.5	3,170.3
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	3,023.5	3,170.3
Total liabilities and partners’ capital	3,505.7	3,523.4
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0	0.0	0.0
Accounts receivable	3.7	0.5
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	3.7	0.5
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investment in consolidated affiliates	0.0	0.0
Investment	1,198.5	1,115.4
Other assets	0.0	0.0
Total assets	1,202.2	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	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	1,002.3	923.4
Interest of non-controlling partners in subsidiary	199.9	192.5
Total partners’ capital	1,202.2	1,115.9
Total liabilities and partners’ capital	1,202.2	1,115.9
Crestwood Midstream Partners LP
Current assets:
Cash	1.1	1.3	$ 0.5	$ 0.1
Accounts receivable	344.7	289.8
Inventory	92.9	66.0
Other	13.0	16.0
Total current assets	451.7	373.1
Property, plant and equipment, net	2,242.2	2,298.4
Intangible Assets, Net (Including Goodwill)	814.0	851.9
Investment in consolidated affiliates	0.0	0.0
Investment	1,198.5	1,115.4
Other assets	2.6	1.8
Total assets	4,709.0	4,640.6
Current liabilities:
Accounts payable	310.0	214.5
Total current liabilities	165.3	117.5
Total current liabilities	475.3	332.0
Long-term liabilities:
Long-term debt, less current portion	1,615.4	1,522.7
Other long-term liabilities	45.3	42.0
Deferred income taxes	0.7	0.7
Partners' capital	2,372.4	2,550.7
Interest of non-controlling partners in subsidiary	199.9	192.5
Total partners’ capital	2,572.3	2,743.2
Total liabilities and partners’ capital	$ 4,709.0	$ 4,640.6