Segments (Reconciliation of Net Income (Loss) to EBITDA) (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)
Segment Reporting, Other Significant Reconciling Item [Line Items]
Number of Operating Segments | segment			3
Net income (loss)	$ (39.6)	$ 4.6	$ (116.0)	$ (43.1)
Interest and debt expense, net	30.9	33.7	102.0	100.3
Provision (benefit) for income taxes	0.1	0.0	0.1	(0.1)
Depreciation, amortization and accretion	64.6	60.8	182.6	177.9
EBITDA	56.0	99.1	175.4	235.0
Loss on modification/extinguishment of debt	0.0	0.0	6.7	0.0
Crestwood Midstream Partners LP
Segment Reporting, Other Significant Reconciling Item [Line Items]
Net income (loss)	(41.8)	2.3	(120.7)	(50.1)
Interest and debt expense, net	30.9	33.7	102.0	100.3
Provision (benefit) for income taxes	0.1	0.0	0.1	(0.2)
Depreciation, amortization and accretion	68.2	64.2	193.2	188.4
EBITDA	57.4	100.2	181.3	238.4
Loss on modification/extinguishment of debt	$ 0.0	$ 0.0	$ 6.7	$ 0.0