Condensed Consolidating Financial Information (Balance Sheet) (Details) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash	$ 6.7	$ 25.7
Accounts receivable	165.9	242.2
Inventory	88.9	53.7
Total current assets	314.6	376.4
Property, plant and equipment, net	3,042.4	2,909.1
Operating lease, right-of-use assets, net	44.2	53.8
Investment	961.9	980.4
Other non-current assets	4.9	5.5
Total assets	5,323.7	5,349.3
Current liabilities:
Accounts payable	118.6	189.2
Total current liabilities	284.8	357.8
Long-term liabilities:
Long-term debt, less current portion	2,575.7	2,328.3
Other long-term liabilities	285.7	301.6
Deferred income taxes	2.3	2.6
Total liabilities	3,148.5	2,990.3
Interest of non-controlling partner in subsidiary	430.6	426.2	$ 424.4	$ 0.0
Total partners’ capital	1,744.6	1,932.8
Total liabilities and capital	5,323.7	5,349.3
Eliminations
Current assets:
Cash	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
Operating lease, right-of-use assets, net	0.0	0.0
Goodwill and intangible assets, net	0.0	0.0
Investment in consolidated affiliates	(4,501.0)	(4,451.6)
Investment	0.0	0.0
Other non-current assets	0.0	0.0
Total assets	(4,501.0)	(4,451.6)
Current liabilities:
Accounts payable	0.0	0.0
Other 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
Total liabilities	0.0	0.0
Interest of non-controlling partner in subsidiary (Note 10)		0.0
Interest of non-controlling partner in subsidiary	0.0
Partners' capital	(4,501.0)	(4,451.6)
Total liabilities and capital	(4,501.0)	(4,451.6)
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Current assets:
Cash	0.4	1.8
Accounts receivable	0.0	0.0
Inventory	0.0	0.0
Other	0.0	0.0
Total current assets	0.4	1.8
Property, plant and equipment, net	0.0	0.0
Operating lease, right-of-use assets, net	0.0	0.0
Goodwill and intangible assets, net	0.0	0.0
Investment in consolidated affiliates	4,501.0	4,451.6
Investment	0.0	0.0
Other non-current assets	0.0	0.0
Total assets	4,501.4	4,453.4
Current liabilities:
Accounts payable	0.0	0.0
Other current liabilities	25.2	25.8
Total current liabilities	25.2	25.8
Long-term liabilities:
Long-term debt, less current portion	2,575.7	2,328.3
Other long-term liabilities	0.0	0.0
Deferred income taxes	0.0	0.0
Total liabilities	2,600.9	2,354.1
Interest of non-controlling partner in subsidiary (Note 10)		0.0
Interest of non-controlling partner in subsidiary	0.0
Partners' capital	1,900.5	2,099.3
Total liabilities and capital	4,501.4	4,453.4
Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	0.0	0.0
Accounts receivable	146.5	229.1
Inventory	88.9	53.7
Other	52.8	54.6
Total current assets	288.2	337.4
Property, plant and equipment, net	2,410.1	2,331.3
Operating lease, right-of-use assets, net	41.5	51.0
Goodwill and intangible assets, net	671.2	650.7
Investment in consolidated affiliates	0.0	0.0
Investment	0.0	0.0
Other non-current assets	2.4	1.9
Total assets	3,413.4	3,372.3
Current liabilities:
Accounts payable	114.6	175.9
Other current liabilities	114.8	123.9
Total current liabilities	229.4	299.8
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	165.8	174.8
Deferred income taxes	0.6	0.7
Total liabilities	395.8	475.3
Interest of non-controlling partner in subsidiary (Note 10)		0.0
Interest of non-controlling partner in subsidiary	0.0
Partners' capital	3,017.6	2,897.0
Total liabilities and capital	3,413.4	3,372.3
Non-Guarantor Subsidiaries | Reportable Legal Entities
Current assets:
Cash	5.7	23.6
Accounts receivable	19.3	12.8
Inventory	0.0	0.0
Other	0.3	0.2
Total current assets	25.3	36.6
Property, plant and equipment, net	783.6	736.2
Operating lease, right-of-use assets, net	2.7	2.8
Goodwill and intangible assets, net	284.5	373.4
Investment in consolidated affiliates	0.0	0.0
Investment	961.9	980.4
Other non-current assets	0.5	0.5
Total assets	2,058.5	2,129.9
Current liabilities:
Accounts payable	1.5	10.7
Other current liabilities	24.8	17.6
Total current liabilities	26.3	28.3
Long-term liabilities:
Long-term debt, less current portion	0.0	0.0
Other long-term liabilities	118.2	120.8
Deferred income taxes	0.0	0.0
Total liabilities	144.5	149.1
Interest of non-controlling partner in subsidiary (Note 10)		426.2
Interest of non-controlling partner in subsidiary	430.6
Partners' capital	1,483.4	1,554.6
Total liabilities and capital	2,058.5	2,129.9
Crestwood Midstream Partners LP
Current assets:
Cash	6.1	25.4
Accounts receivable	165.8	241.9
Inventory	88.9	53.7
Other	53.1	54.8
Total current assets	313.9	375.8
Property, plant and equipment, net	3,193.7	3,067.5
Operating lease, right-of-use assets, net	44.2	53.8
Goodwill and intangible assets, net	955.7	1,024.1
Investment in consolidated affiliates	0.0	0.0
Investment	961.9	980.4
Other non-current assets	2.9	2.4
Total assets	5,472.3	5,504.0
Current liabilities:
Accounts payable	116.1	186.6
Other current liabilities	164.8	167.3
Total current liabilities	280.9	353.9
Long-term liabilities:
Long-term debt, less current portion	2,575.7	2,328.3
Other long-term liabilities	284.0	295.6
Deferred income taxes	0.6	0.7
Total liabilities	3,141.2	2,978.5
Interest of non-controlling partner in subsidiary (Note 10)		426.2
Interest of non-controlling partner in subsidiary	430.6
Partners' capital	1,900.5	2,099.3
Total liabilities and capital	$ 5,472.3	$ 5,504.0