Segments (Summary Of Segment Information) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($) segment	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Net income (loss)	$ (23.4)	$ 14.1
Interest and debt expense, net	$ 32.6	24.9
Number of Operating Segments | segment	3
Depreciation, amortization and accretion	$ 56.1	39.8
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	727.9	835.2
Intersegment Revenues	0.0	0.0
Costs of product/services sold	534.4	695.6
Operations and maintenance	37.6	28.6
General and administrative	14.9	37.2
Gain (loss) on long-lived assets	(1.0)	(2.0)
Goodwill impairment	(80.3)	0.0
Earnings from unconsolidated affiliates, net	5.5	6.9
Other income, net	0.1	0.1
EBITDA	65.3	78.8
Goodwill	138.6		$ 218.9
Total assets	5,177.1		5,349.3
Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	214.9	182.3
Intersegment Revenues	40.0	52.8
Costs of product/services sold	108.3	138.0
Operations and maintenance	27.0	18.1
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	(1.0)	(1.8)
Goodwill impairment	(80.3)
Earnings from unconsolidated affiliates, net	0.8	(0.2)
Other income, net	0.0	0.0
EBITDA	39.1	77.0
Goodwill	45.9
Total assets	3,633.8
Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	3.5	7.8
Intersegment Revenues	2.6	3.6
Costs of product/services sold	0.2	0.0
Operations and maintenance	1.4	1.0
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	0.0	0.0
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	4.7	7.1
Other income, net	0.0	0.0
EBITDA	9.2	17.5
Goodwill	0.0
Total assets	973.7
Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	509.5	645.1
Intersegment Revenues	(42.6)	(56.4)
Costs of product/services sold	425.9	557.6
Operations and maintenance	9.2	9.5
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	0.0	(0.2)
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
Other income, net	0.0	0.0
EBITDA	31.8	21.4
Goodwill	92.7
Total assets	531.0
Corporate
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	0.0	0.0
Intersegment Revenues	0.0	0.0
Costs of product/services sold	0.0	0.0
Operations and maintenance	0.0	0.0
General and administrative	14.9	37.2
Gain (loss) on long-lived assets	0.0	0.0
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
Other income, net	0.1	0.1
EBITDA	(14.8)	(37.1)
Goodwill	0.0
Total assets	38.6
Crestwood Midstream Partners LP
Net income (loss)	(25.6)	11.6
Interest and debt expense, net	32.6	24.9
Depreciation, amortization and accretion	59.6	43.4
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	727.9	835.2
Intersegment Revenues	0.0	0.0
Costs of product/services sold	534.4	695.6
Operations and maintenance	37.6	28.6
General and administrative	13.5	36.0
Gain (loss) on long-lived assets	(1.0)	(2.0)
Goodwill impairment	(80.3)	0.0
Earnings from unconsolidated affiliates, net	5.5	6.9
EBITDA	66.6	79.9
Goodwill	138.6		218.9
Total assets	5,329.3		$ 5,504.0
Crestwood Midstream Partners LP | Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	214.9	182.3
Intersegment Revenues	40.0	52.8
Costs of product/services sold	108.3	138.0
Operations and maintenance	27.0	18.1
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	(1.0)	(1.8)
Goodwill impairment	(80.3)
Earnings from unconsolidated affiliates, net	0.8	(0.2)
EBITDA	39.1	77.0
Goodwill	45.9
Total assets	3,789.7
Crestwood Midstream Partners LP | Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	3.5	7.8
Intersegment Revenues	2.6	3.6
Costs of product/services sold	0.2	0.0
Operations and maintenance	1.4	1.0
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	0.0	0.0
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	4.7	7.1
EBITDA	9.2	17.5
Goodwill	0.0
Total assets	973.7
Crestwood Midstream Partners LP | Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	509.5	645.1
Intersegment Revenues	(42.6)	(56.4)
Costs of product/services sold	425.9	557.6
Operations and maintenance	9.2	9.5
General and administrative	0.0	0.0
Gain (loss) on long-lived assets	0.0	(0.2)
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
EBITDA	31.8	21.4
Goodwill	92.7
Total assets	531.0
Crestwood Midstream Partners LP | Corporate
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	0.0	0.0
Intersegment Revenues	0.0	0.0
Costs of product/services sold	0.0	0.0
Operations and maintenance	0.0	0.0
General and administrative	13.5	36.0
Gain (loss) on long-lived assets	0.0	0.0
Goodwill impairment	0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
EBITDA	(13.5)	$ (36.0)
Goodwill	0.0
Total assets	$ 34.9