Segments (Summary Of Segment Information) (Details) $ in Millions	1 Months Ended	3 Months Ended		9 Months Ended
	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) segment	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Net income (loss)		$ (27.9)	$ 3.0	$ (47.0)	$ (127.8)
Interest and debt expense, net		24.2	27.5	74.8	97.9
Gains (Losses) on Extinguishment of Debt	$ 10.0	0.0	0.0	$ 37.7	(10.0)
Number of Operating Segments | segment				3
Benefit for income taxes		0.1	0.2	$ 0.0	0.2
Depreciation, amortization and accretion		48.1	50.3	145.2	177.0
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		955.6	587.6	2,634.0	1,725.5
Intersegment Revenues		0.0	0.0	0.0	0.0
Costs of product/services sold		858.5	466.7	2,271.6	1,280.1
Operations and maintenance		35.5	33.1	103.4	119.9
General and administrative		22.5	18.3	71.6	70.2
Gain (loss) on long-lived assets		(6.3)	(2.1)	(6.3)	(34.8)
Goodwill impairment		0.0	0.0	0.0	(109.7)
Earnings from unconsolidated affiliates, net		11.5	13.4	29.2	26.1
Other income, net		0.2	0.2	0.4	0.4
EBITDA		44.5	81.0	210.7	137.3
Goodwill		199.0		199.0		$ 199.0
Total assets		4,525.3		4,525.3		4,448.9
Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		434.4	279.3	1,208.1	787.7
Intersegment Revenues		29.9	24.8	94.3	75.9
Costs of product/services sold		378.6	226.1	1,049.9	632.2
Operations and maintenance		16.2	17.4	51.8	56.1
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		(3.9)	(2.0)	(3.9)	(2.0)
Goodwill impairment					(8.6)
Earnings from unconsolidated affiliates, net		4.3	5.5	7.7	16.5
Other income, net		0.0	0.0	0.0	0.0
EBITDA		69.9	64.1	204.5	181.2
Goodwill		45.9		45.9
Total assets		2,452.2		2,452.2
Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		6.2	18.3	24.7	131.5
Intersegment Revenues		1.2	1.5	4.7	3.0
Costs of product/services sold		0.2	0.1	0.3	4.9
Operations and maintenance		1.0	2.5	3.4	18.2
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		0.0	(0.1)	0.0	(32.8)
Goodwill impairment					(13.7)
Earnings from unconsolidated affiliates, net		7.2	7.9	21.5	9.6
Other income, net		0.0	0.0	0.0	0.0
EBITDA		13.4	25.0	47.2	74.5
Goodwill		0.0		0.0
Total assets		1,049.9		1,049.9
Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		515.0	290.0	1,401.2	806.3
Intersegment Revenues		(31.1)	(26.3)	(99.0)	(78.9)
Costs of product/services sold		479.7	240.5	1,221.4	643.0
Operations and maintenance		18.3	13.2	48.2	45.6
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		0.6	0.0	0.6	0.0
Goodwill impairment					(87.4)
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0	0.0
Other income, net		0.0	0.0	0.0	0.0
EBITDA		(13.5)	10.0	33.2	(48.6)
Goodwill		153.1		153.1
Total assets		1,002.3		1,002.3
Corporate
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		0.0	0.0	0.0	0.0
Intersegment 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		22.5	18.3	71.6	70.2
Gain (loss) on long-lived assets		(3.0)	0.0	(3.0)	0.0
Goodwill impairment					0.0
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0	0.0
Other income, net		0.2	0.2	0.4	0.4
EBITDA		(25.3)	(18.1)	(74.2)	(69.8)
Goodwill		0.0		0.0
Total assets		20.9		20.9
Crestwood Midstream Partners LP
Net income (loss)		(29.8)	0.6	(53.1)	(130.3)
Interest and debt expense, net		24.2	27.5	74.8	97.9
Gains (Losses) on Extinguishment of Debt		0.0	0.0	37.7	(10.0)
Benefit for income taxes		0.1	0.0	0.0	0.0
Depreciation, amortization and accretion		50.9	53.2	153.5	185.2
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		955.6	587.6	2,634.0	1,725.5
Intersegment Revenues		0.0	0.0	0.0	0.0
Costs of product/services sold		858.5	466.7	2,271.6	1,280.1
Operations and maintenance		35.5	33.6	103.4	116.7
General and administrative		21.4	17.3	69.0	67.5
Gain (loss) on long-lived assets		(6.3)	(2.1)	(6.3)	(34.8)
Goodwill impairment		0.0	0.0	0.0	(109.7)
Earnings from unconsolidated affiliates, net		11.5	13.4	29.2	26.1
EBITDA		45.4	81.3	212.9	142.8
Goodwill		199.0		199.0		199.0
Total assets		4,709.0		4,709.0		$ 4,640.6
Crestwood Midstream Partners LP | Gathering and Processing Operations
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		434.4	279.3	1,208.1	787.7
Intersegment Revenues		29.9	24.8	94.3	75.9
Costs of product/services sold		378.6	226.1	1,049.9	632.2
Operations and maintenance		16.2	17.4	51.8	56.1
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		(3.9)	(2.0)	(3.9)	(2.0)
Goodwill impairment					(8.6)
Earnings from unconsolidated affiliates, net		4.3	5.5	7.7	16.5
EBITDA		69.9	64.1	204.5	181.2
Goodwill		45.9		45.9
Total assets		2,643.7		2,643.7
Crestwood Midstream Partners LP | Storage and Transportation
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		6.2	18.3	24.7	131.5
Intersegment Revenues		1.2	1.5	4.7	3.0
Costs of product/services sold		0.2	0.1	0.3	4.9
Operations and maintenance		1.0	3.0	3.4	15.0
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		0.0	(0.1)	0.0	(32.8)
Goodwill impairment					(13.7)
Earnings from unconsolidated affiliates, net		7.2	7.9	21.5	9.6
EBITDA		13.4	24.5	47.2	77.7
Goodwill		0.0		0.0
Total assets		1,049.9		1,049.9
Crestwood Midstream Partners LP | Marketing Supply and Logistics
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		515.0	290.0	1,401.2	806.3
Intersegment Revenues		(31.1)	(26.3)	(99.0)	(78.9)
Costs of product/services sold		479.7	240.5	1,221.4	643.0
Operations and maintenance		18.3	13.2	48.2	45.6
General and administrative		0.0	0.0	0.0	0.0
Gain (loss) on long-lived assets		0.6	0.0	0.6	0.0
Goodwill impairment					(87.4)
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0	0.0
EBITDA		(13.5)	10.0	33.2	(48.6)
Goodwill		153.1		153.1
Total assets		1,002.3		1,002.3
Crestwood Midstream Partners LP | Corporate
Segment Reporting Information, Additional Information [Abstract]
Operating revenues		0.0	0.0	0.0	0.0
Intersegment 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		21.4	17.3	69.0	67.5
Gain (loss) on long-lived assets		(3.0)	0.0	(3.0)	0.0
Goodwill impairment					0.0
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0	0.0
EBITDA		(24.4)	$ (17.3)	(72.0)	$ (67.5)
Goodwill		0.0		0.0
Total assets		$ 13.1		$ 13.1