Certain Balance Sheet Information (Accrued Expenses and Other Liabilities) (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Apr. 30, 2016	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accrued Expenses and Other Liabilities [Line Items]
Net proceeds from sale of assets	$ 945.0	$ 943.1	$ 2.9
Payments to acquire equity method investments		6.2	40.0
Accrued expenses		36.8		$ 46.4
Accrued property taxes		6.7		4.8
Accrued product purchases payable		5.2		1.5
Tax payable		0.3		0.5
Interest payable		32.8		26.2
Accrued additions to property, plant and equipment		2.6		10.4
Capital leases		1.5		1.6
Deferred revenue		27.6		14.2
Total accrued expenses and other liabilities		113.5		105.6
CEGP
Accrued Expenses and Other Liabilities [Line Items]
Net proceeds from sale of assets		30.0
Crestwood Midstream Partners LP
Accrued Expenses and Other Liabilities [Line Items]
Net proceeds from sale of assets		943.1	2.9
Payments to acquire equity method investments		6.2	$ 39.8
Accrued expenses		35.3		44.1
Accrued property taxes		6.7		4.8
Accrued product purchases payable		5.2		1.5
Tax payable		0.2		0.5
Interest payable		32.8		26.2
Accrued additions to property, plant and equipment		2.6		10.4
Capital leases		1.5		1.6
Deferred revenue		27.6		14.2
Total accrued expenses and other liabilities		$ 111.9		$ 103.3