Segments (Summary Of Segment Information) (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Net income	$ 12.1	$ (43.0)	$ 205.6	$ 18.6
Segment Reporting Information, Additional Information [Abstract]
Total revenues	1,139.4	1,566.0	3,423.7	4,597.8
Costs of product/services sold	901.6	1,286.8	2,683.6	3,864.4
Operations and maintenance	56.9	55.0	166.7	144.0
General and administrative	30.2	33.9	86.8	103.8
Gain (loss) on long-lived assets	(2.6)	(175.9)	(4.8)	(186.9)
Gain on acquisition	0.0	75.3	0.0	75.3
Earnings from unconsolidated affiliates, net	1.1	3.2	135.2	12.2
Other income, net	0.2	0.0	0.3	0.2
EBITDA	149.4	92.9	617.3	386.4
Assets	6,359.8		6,359.8		$ 6,567.0
Intersegment Eliminations
Segment Reporting Information, Additional Information [Abstract]
Total revenues	(123.4)	(280.0)	(350.2)	(559.0)
Eliminations
Segment Reporting Information, Additional Information [Abstract]
Gain (Loss) on Disposition of Assets				53.0
Gathering and Processing North | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	333.7	414.8	948.1	1,208.4
Gathering and Processing South | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	175.5	315.2	492.5	381.2
Storage and Logistics | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	753.6	1,116.0	2,333.3	3,567.2
Crestwood Midstream Partners LP
Net income	21.4	(113.0)	217.8	(107.4)
Segment Reporting Information, Additional Information [Abstract]
Total revenues	1,139.4	1,566.0	3,423.7	4,597.8
Costs of product/services sold	901.6	1,286.8	2,683.6	3,864.4
Operations and maintenance	56.9	55.0	166.7	144.0
General and administrative	20.8	32.3	74.6	99.0
Gain (loss) on long-lived assets	(2.6)	(247.6)	(4.8)	(311.9)
Gain on acquisition	0.0	75.3	0.0	75.3
Earnings from unconsolidated affiliates, net	1.1	3.2	135.2	12.2
EBITDA	158.6	22.8	629.2	266.0
Assets	6,354.2		6,354.2		6,561.4
Crestwood Midstream Partners LP | Corporate, Non-Segment
Segment Reporting Information, Additional Information [Abstract]
Total revenues	0.0	0.0	0.0	0.0
Costs of product/services sold	0.0	0.0	0.0	0.0
Operations and maintenance	0.0	0.0	0.0	0.0
General and administrative	20.8	32.3	74.6	99.0
Gain (loss) on long-lived assets	0.0	0.0	0.4	0.0
Gain on acquisition		0.0		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0	0.0	0.0
EBITDA	(20.8)	(32.3)	(74.2)	(99.0)
Assets	34.4		34.4		27.2
Crestwood Midstream Partners LP | Corporate and Eliminations
Segment Reporting Information, Additional Information [Abstract]
Total revenues	0.0	0.0	0.0	0.0
Crestwood Midstream Partners LP | Gathering and Processing North | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	262.8	272.6	717.1	787.2
Costs of product/services sold	158.4	230.2	447.7	686.6
Operations and maintenance	29.9	27.4	85.6	78.6
General and administrative	0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets	0.0	0.0	0.1	0.0
Gain on acquisition		0.0		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0	0.0	0.0
EBITDA	145.4	157.2	414.9	443.2
Assets	3,921.3		3,921.3		4,003.6
Crestwood Midstream Partners LP | Gathering and Processing North | Intersegment Eliminations
Segment Reporting Information, Additional Information [Abstract]
Total revenues	70.9	142.2	231.0	421.2
Crestwood Midstream Partners LP | Gathering and Processing South | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	123.0	177.4	373.3	243.4
Costs of product/services sold	121.1	249.6	329.8	249.6
Operations and maintenance	14.9	14.3	45.2	28.6
General and administrative	0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets	0.0	(247.6)	(2.7)	(307.8)
Gain on acquisition		75.3		75.3
Earnings from unconsolidated affiliates, net	1.1	2.0	2.0	9.4
EBITDA	40.6	(119.0)	116.8	(120.1)
Assets	1,452.4		1,452.4		1,473.0
Crestwood Midstream Partners LP | Gathering and Processing South | Intersegment Eliminations
Segment Reporting Information, Additional Information [Abstract]
Total revenues	52.5	137.8	119.2	137.8
Crestwood Midstream Partners LP | Storage and Logistics | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
Total revenues	753.6	1,116.0	2,333.3	3,567.2
Costs of product/services sold	622.1	807.0	1,906.1	2,928.2
Operations and maintenance	12.1	13.3	35.9	36.8
General and administrative	0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets	(2.6)	0.0	(2.6)	(4.1)
Gain on acquisition		0.0		0.0
Earnings from unconsolidated affiliates, net	0.0	1.2	133.2	2.8
EBITDA	(6.6)	16.9	171.7	41.9
Assets	946.1		946.1		1,057.6
Crestwood Midstream Partners LP | Storage and Logistics | Intersegment Eliminations
Segment Reporting Information, Additional Information [Abstract]
Total revenues	(123.4)	(280.0)	(350.2)	(559.0)
Crestwood Equity Partners LP
Segment Reporting Information, Additional Information [Abstract]
General and administrative	9.4	1.6	12.2	4.8
Elimination of Loss on Long-Lived Assets		71.7		125.0
Other income, net	0.2		0.3	0.2
EBITDA	149.4	92.9	617.3	386.4
Assets	6,359.8		6,359.8		6,567.0
Crestwood Equity Partners LP | Barnett Shale Assets
Segment Reporting Information, Additional Information [Abstract]
Gain (Loss) on Disposition of Assets				72.0
Crestwood Equity Partners LP | Corporate, Non-Segment
Segment Reporting Information, Additional Information [Abstract]
General and administrative	9.4	1.6	12.2	4.8
Elimination of Loss on Long-Lived Assets		0.0		0.0
Other income, net	0.2		0.3	0.2
EBITDA	(30.0)	(33.9)	(86.1)	(103.6)
Assets	40.0		40.0		32.8
Crestwood Equity Partners LP | Gathering and Processing North | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
General and administrative	0.0	0.0	0.0	0.0
Elimination of Loss on Long-Lived Assets		0.0		0.0
Other income, net	0.0		0.0	0.0
EBITDA	145.4	157.2	414.9	443.2
Assets	3,921.3		3,921.3		4,003.6
Crestwood Equity Partners LP | Gathering and Processing South | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
General and administrative	0.0	0.0	0.0	0.0
Elimination of Loss on Long-Lived Assets		71.7		125.0
Other income, net	0.0		0.0	0.0
EBITDA	40.6	(47.3)	116.8	4.9
Assets	1,452.4		1,452.4		1,473.0
Crestwood Equity Partners LP | Storage and Logistics | Operating Segments
Segment Reporting Information, Additional Information [Abstract]
General and administrative	0.0	0.0	0.0	0.0
Elimination of Loss on Long-Lived Assets		0.0		0.0
Other income, net	0.0		0.0	0.0
EBITDA	(6.6)	$ 16.9	171.7	$ 41.9
Assets	$ 946.1		$ 946.1		$ 1,057.6