Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014	Dec. 31, 2012
Current assets:
Cash	$ 1.1	$ 0.5	$ 67.7		$ 8.8
Accounts receivable	209.6	236.5
Inventory	26.6	44.5
Total current assets	272.4	335.8
Property, plant and equipment, net	3,303.0	3,310.8
Investment	260.6	254.3
Other assets	8.0	7.2
Total assets	5,570.0	5,762.8
Current liabilities:
Accounts payable	119.1	144.1
Total current liabilities	224.1	258.2
Long-term liabilities:
Long-term debt, less current portion (Note 7)	2,530.8	2,501.8
Other long-term liabilities	48.2	47.5
Deferred income taxes	8.3	8.4
Total partners’ capital	2,758.6	2,946.9
Total liabilities and partners’ capital	5,570.0	5,762.8
Crestwood Midstream Partners LP
Current assets:
Cash	0.8	0.1	67.4	$ 7.6	$ 7.6
Accounts receivable	209.6	236.5
Inventory	26.6	44.5
Other	33.3	52.5
Total current assets	270.3	333.6
Property, plant and equipment, net	3,514.4	3,525.7
Intangible Assets, Net (Including Goodwill)	1,719.1	1,846.9
Investment in consolidated affiliates	0.0	0.0
Investment	260.6	254.3
Other assets	3.0	3.1
Total assets	5,767.4	5,963.6
Current liabilities:
Accounts payable	116.5	141.4
Total current liabilities	102.8	111.6
Total current liabilities	219.3	253.0
Long-term liabilities:
Long-term debt, less current portion (Note 7)	2,530.8	2,501.8
Other long-term liabilities	44.1	43.3
Deferred income taxes	0.6	0.4
Partners' capital	2,787.0	2,981.6
Interest of non-controlling partners in subsidiary	185.6	183.5
Total partners’ capital	2,972.6	3,165.1
Total liabilities and partners’ capital	5,767.4	5,963.6
Crestwood Midstream Partners LP | Parent Company
Current assets:
Cash	0.8	0.1	0.0	0.0
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	0.8	0.1
Property, plant and equipment, net	0.0	0.0
Intangible Assets, Net (Including Goodwill)	0.0	0.0
Investment in consolidated affiliates	5,350.2	5,506.8
Investment	0.0	0.0
Other assets	0.0	0.0
Total assets	5,351.0	5,506.9
Current liabilities:
Accounts payable	0.0	0.0
Total current liabilities	35.8	26.4
Total current liabilities	35.8	26.4
Long-term liabilities:
Long-term debt, less current portion (Note 7)	2,528.2	2,498.9
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	2,787.0	2,981.6
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	2,787.0	2,981.6
Total liabilities and partners’ capital	5,351.0	5,506.9
Crestwood Midstream Partners LP | Guarantor Subsidiaries
Current assets:
Cash	0.0	0.0	67.4	7.6
Accounts receivable	209.1	236.0
Inventory	26.6	44.5
Other	33.3	52.5
Total current assets	269.0	333.0
Property, plant and equipment, net	3,514.4	3,525.7
Intangible Assets, Net (Including Goodwill)	1,719.1	1,846.9
Investment in consolidated affiliates	0.0	0.0
Investment	0.0	0.0
Other assets	3.0	3.1
Total assets	5,505.5	5,708.7
Current liabilities:
Accounts payable	116.5	141.3
Total current liabilities	67.0	85.2
Total current liabilities	183.5	226.5
Long-term liabilities:
Long-term debt, less current portion (Note 7)	2.6	2.9
Other long-term liabilities	44.1	43.3
Deferred income taxes	0.6	0.4
Partners' capital	5,274.7	5,435.6
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	5,274.7	5,435.6
Total liabilities and partners’ capital	5,505.5	5,708.7
Crestwood Midstream Partners LP | Non-Guarantor Subsidiaries
Current assets:
Cash	0.0	0.0	0.0	0.0
Accounts receivable	0.5	0.5
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	0.5	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	260.6	254.3
Other assets	0.0	0.0
Total assets	261.1	254.8
Current liabilities:
Accounts payable	0.0	0.1
Total current liabilities	0.0	0.0
Total current liabilities	0.0	0.1
Long-term liabilities:
Long-term debt, less current portion (Note 7)	0.0	0.0
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	75.5	71.2
Interest of non-controlling partners in subsidiary	185.6	183.5
Total partners’ capital	261.1	254.7
Total liabilities and partners’ capital	261.1	254.8
Crestwood Midstream Partners LP | 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	(5,350.2)	(5,506.8)
Investment	0.0	0.0
Other assets	0.0	0.0
Total assets	(5,350.2)	(5,506.8)
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 (Note 7)	0.0	0.0
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Partners' capital	(5,350.2)	(5,506.8)
Interest of non-controlling partners in subsidiary	0.0	0.0
Total partners’ capital	(5,350.2)	(5,506.8)
Total liabilities and partners’ capital	$ (5,350.2)	$ (5,506.8)