Segments (Summary Of Segment Information) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2016 USD ($) segment	Mar. 31, 2015 USD ($)	Dec. 31, 2015 USD ($)
Interest and debt expense, net	$ 36.1	$ 33.6
Number of Operating Segments | segment	3
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	$ 536.0	731.5
Intersegment Revenues	0.0	0.0
Costs of product/services sold	363.4	529.7
Operations and maintenance	41.8	50.6
General and administrative	23.0	27.5
Goodwill impairment	(109.7)	0.0
Loss on long-lived assets, net	0.0	(1.0)
Earnings from unconsolidated affiliates, net	6.5	3.4
Other income, net	0.1	0.2
EBITDA	4.7	126.3
Goodwill	975.8		$ 1,085.5
Total assets	5,570.0		5,762.8
Cash expenditures for property, plant and equipment	55.6	47.4
Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	238.9	350.3
Intersegment Revenues	20.5	10.1
Costs of product/services sold	179.8	266.7
Operations and maintenance	17.8	24.1
General and administrative	0.0	0.0
Goodwill impairment	(8.6)
Loss on long-lived assets, net		(0.3)
Earnings from unconsolidated affiliates, net	5.1	2.5
Other income, net	0.0	0.0
EBITDA	58.3	71.8
Goodwill	45.9
Total assets	2,321.2
Cash expenditures for property, plant and equipment	44.3	36.2
Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	59.4	67.6
Intersegment Revenues	0.4	0.0
Costs of product/services sold	2.9	5.3
Operations and maintenance	7.2	6.4
General and administrative	0.0	0.0
Goodwill impairment	(13.7)
Loss on long-lived assets, net		(0.7)
Earnings from unconsolidated affiliates, net	1.4	0.9
Other income, net	0.0	0.0
EBITDA	37.4	56.1
Goodwill	757.5
Total assets	2,185.7
Cash expenditures for property, plant and equipment	3.3	4.1
Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	237.7	313.6
Intersegment Revenues	(20.9)	(10.1)
Costs of product/services sold	180.7	257.7
Operations and maintenance	16.8	20.1
General and administrative	0.0	0.0
Goodwill impairment	(87.4)
Loss on long-lived assets, net		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
Other income, net	0.0	0.0
EBITDA	(68.1)	25.7
Goodwill	172.4
Total assets	924.4
Cash expenditures for property, plant and equipment	7.1	6.9
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	23.0	27.5
Goodwill impairment	0.0
Loss on long-lived assets, net		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
Other income, net	0.1	0.2
EBITDA	(22.9)	(27.3)
Goodwill	0.0
Total assets	138.7
Cash expenditures for property, plant and equipment	0.9	0.2
Crestwood Midstream Partners LP
Interest and debt expense, net	36.1	29.9
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	536.0	731.5
Intersegment Revenues	0.0	0.0
Costs of product/services sold	363.4	529.7
Operations and maintenance	41.7	50.6
General and administrative	22.2	25.6
Goodwill impairment	(109.7)	0.0
Loss on long-lived assets, net	0.0	(0.8)
Earnings from unconsolidated affiliates, net	6.5	3.4
EBITDA	5.5	128.2
Goodwill	975.8		1,085.5
Total assets	5,767.4		$ 5,963.6
Cash expenditures for property, plant and equipment	55.6	47.4
Crestwood Midstream Partners LP | Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	238.9	350.3
Intersegment Revenues	20.5	10.1
Costs of product/services sold	179.8	266.7
Operations and maintenance	17.8	24.1
General and administrative	0.0	0.0
Goodwill impairment	(8.6)
Loss on long-lived assets, net		(0.3)
Earnings from unconsolidated affiliates, net	5.1	2.5
EBITDA	58.3	71.8
Goodwill	45.9
Total assets	2,534.1
Cash expenditures for property, plant and equipment	44.3	36.2
Crestwood Midstream Partners LP | Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	59.4	67.6
Intersegment Revenues	0.4	0.0
Costs of product/services sold	2.9	5.3
Operations and maintenance	7.1	6.4
General and administrative	0.0	0.0
Goodwill impairment	(13.7)
Loss on long-lived assets, net		(0.5)
Earnings from unconsolidated affiliates, net	1.4	0.9
EBITDA	37.5	56.3
Goodwill	757.5
Total assets	2,185.0
Cash expenditures for property, plant and equipment	3.3	4.1
Crestwood Midstream Partners LP | Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues	237.7	313.6
Intersegment Revenues	(20.9)	(10.1)
Costs of product/services sold	180.7	257.7
Operations and maintenance	16.8	20.1
General and administrative	0.0	0.0
Goodwill impairment	(87.4)
Loss on long-lived assets, net		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
EBITDA	(68.1)	25.7
Goodwill	172.4
Total assets	924.4
Cash expenditures for property, plant and equipment	7.1	6.9
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	22.2	25.6
Goodwill impairment	0.0
Loss on long-lived assets, net		0.0
Earnings from unconsolidated affiliates, net	0.0	0.0
EBITDA	(22.2)	(25.6)
Goodwill	0.0
Total assets	123.9
Cash expenditures for property, plant and equipment	$ 0.9	$ 0.2