Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 31, 2018
Current assets:
Cash	$ 25.7	$ 0.9
Restricted cash	0.0	16.3
Accounts receivable	242.2	251.5
Inventory	53.7	64.6
Total current assets	376.4	379.3
Property, plant and equipment, net	2,909.1	2,029.7
Operating lease right-of-use assets, net	53.8
Investments in unconsolidated affiliates	980.4	1,188.2
Other non-current assets	5.5	4.9
Total assets	5,349.3	4,294.5
Current liabilities:
Accounts payable	189.2	213.0
Total current liabilities	357.8	332.1
Long-term liabilities:
Long-term debt, less current portion	2,328.3	1,752.4
Other long-term liabilities	301.6	173.6
Deferred income taxes	2.6	2.6
Liabilities	2,990.3	2,260.7
Interest of non-controlling partner in subsidiary (Note 12)		181.3
Partners' Capital	1,932.8	1,852.5
Total partners’ capital	1,932.8	2,033.8
Total liabilities and capital	5,349.3	4,294.5
Eliminations
Current assets:
Cash	0.0	0.0
Restricted cash		0.0
Accounts receivable	0.0	(16.3)
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	0.0	(16.3)
Property, plant and equipment, net	0.0	0.0
Goodwill and intangible assets, net	0.0	0.0
Operating lease right-of-use assets, net	0.0
Investments in consolidated affiliates	(4,451.6)	(3,800.4)
Investments in unconsolidated affiliates	0.0	0.0
Other non-current assets	0.0	0.0
Total assets	(4,451.6)	(3,816.7)
Current liabilities:
Accounts payable	0.0	(16.3)
Total current liabilities	0.0	0.0
Total current liabilities	0.0	(16.3)
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
Liabilities	0.0	(16.3)
Interest of non-controlling partner in subsidiary (Note 12)	0.0	0.0
Partners' Capital	(4,451.6)	(3,800.4)
Total partners’ capital		(3,800.4)
Total liabilities and capital	(4,451.6)	(3,816.7)
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Current assets:
Cash	1.8	0.2
Restricted cash		16.3
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	1.8	16.5
Property, plant and equipment, net	0.0	0.0
Goodwill and intangible assets, net	0.0	0.0
Operating lease right-of-use assets, net	0.0
Investments in consolidated affiliates	4,451.6	3,800.4
Investments in unconsolidated affiliates	0.0	0.0
Other non-current assets	0.0	0.0
Total assets	4,453.4	3,816.9
Current liabilities:
Accounts payable	0.0	16.3
Total current liabilities	25.8	20.0
Total current liabilities	25.8	36.3
Long-term liabilities:
Long-term debt, less current portion	2,328.3	1,752.4
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Liabilities	2,354.1	1,788.7
Interest of non-controlling partner in subsidiary (Note 12)	0.0	0.0
Partners' Capital	2,099.3	2,028.2
Total partners’ capital		2,028.2
Total liabilities and capital	4,453.4	3,816.9
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0
Restricted cash		0.0
Accounts receivable	229.1	246.3
Inventory	53.7	64.6
Other	54.6	46.0
Total current assets	337.4	356.9
Property, plant and equipment, net	2,331.3	2,202.3
Goodwill and intangible assets, net	650.7	692.4
Operating lease right-of-use assets, net	51.0
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	0.0	0.0
Other non-current assets	1.9	2.1
Total assets	3,372.3	3,253.7
Current liabilities:
Accounts payable	175.9	210.5
Total current liabilities	123.9	81.8
Total current liabilities	299.8	292.3
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	174.8	114.0
Deferred income taxes	0.7	0.6
Liabilities	475.3	406.9
Interest of non-controlling partner in subsidiary (Note 12)	0.0	0.0
Partners' Capital	2,897.0	2,846.8
Total partners’ capital		2,846.8
Total liabilities and capital	3,372.3	3,253.7
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	23.6	0.0
Restricted cash		0.0
Accounts receivable	12.8	19.9
Inventory	0.0	0.0
Other	0.2	0.0
Total current assets	36.6	19.9
Property, plant and equipment, net	736.2	0.0
Goodwill and intangible assets, net	373.4	0.0
Operating lease right-of-use assets, net	2.8
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	980.4	1,188.2
Other non-current assets	0.5	0.0
Total assets	2,129.9	1,208.1
Current liabilities:
Accounts payable	10.7	0.0
Total current liabilities	17.6	16.2
Total current liabilities	28.3	16.2
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	120.8	57.0
Deferred income taxes	0.0	0.0
Liabilities	149.1	73.2
Interest of non-controlling partner in subsidiary (Note 12)	426.2	181.3
Partners' Capital	1,554.6	953.6
Total partners’ capital		1,134.9
Total liabilities and capital	2,129.9	1,208.1
CMLP
Current assets:
Cash	25.4	0.2
Restricted cash		16.3
Accounts receivable	241.9	249.9
Inventory	53.7	64.6
Other	54.8	46.0
Total current assets	375.8	377.0
Property, plant and equipment, net	3,067.5	2,202.3
Goodwill and intangible assets, net	1,024.1	692.4
Operating lease right-of-use assets, net	53.8
Investments in consolidated affiliates	0.0	0.0
Investments in unconsolidated affiliates	980.4	1,188.2
Other non-current assets	2.4	2.1
Total assets	5,504.0	4,462.0
Current liabilities:
Accounts payable	186.6	210.5
Total current liabilities	167.3	118.0
Total current liabilities	353.9	328.5
Long-term liabilities:
Long-term debt, less current portion	2,328.3	1,752.4
Other long-term liabilities	295.6	171.0
Deferred income taxes	0.7	0.6
Liabilities	2,978.5	2,252.5
Interest of non-controlling partner in subsidiary (Note 12)	426.2	181.3
Partners' Capital	2,099.3	2,028.2
Total partners’ capital		2,209.5
Total liabilities and capital	$ 5,504.0	$ 4,462.0