Investments in Unconsolidated Affiliates Narrative (Details) $ in Millions		1 Months Ended		3 Months Ended		9 Months Ended
	Jun. 21, 2017 USD ($)	Oct. 31, 2017 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) a miles	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($) a miles	Sep. 30, 2016 USD ($)	Aug. 01, 2017	Dec. 31, 2016 USD ($)
Schedule of Equity Method Investments [Line Items]
Net proceeds from sale of assets			$ 945.0			$ 1.3	$ 943.1
Investments in unconsolidated affiliates				$ 1,198.5		1,198.5			$ 1,115.4
Contribution of property	$ 69.4
Estimated cost to build						180.0
Payments to Acquire Property, Plant, and Equipment						$ 134.4	$ 79.3
Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Miles of pipeline | miles				60		60
Receipt point meters				20		20
Jackalope Gas Gathering Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates				$ 186.2		$ 186.2			197.2
Tres Palacios Holdings LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates				34.7		34.7			39.0
Powder River Basin Industrial Complex, LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates				8.6		8.6			8.7
Crestwood Permian Basin Holdings LLC
Schedule of Equity Method Investments [Line Items]
Investments in unconsolidated affiliates				114.7		114.7			(0.5)
Stagecoach Gas Services LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage					50.00%		50.00%
Net proceeds from sale of assets							$ 3.0
Contingent consideration, current liability				57.0		57.0
Investments in unconsolidated affiliates				854.3		$ 854.3			871.0
Deconsolidation, gain (loss), amount							32.9
Crestwood Permian Basin LLC
Schedule of Equity Method Investments [Line Items]
Equity interest						100.00%
Crestwood Equity Partners LP
Schedule of Equity Method Investments [Line Items]
Interest, taxes, depreciation and amortization included in earnings from equity method investments				$ 10.0	$ 8.3	$ 25.7	15.3
Crestwood Equity Partners LP | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Ownership percentage				50.00%		50.00%
Crestwood New Mexico Pipeline LLC
Schedule of Equity Method Investments [Line Items]
Equity interest	100.00%
Crestwood Midstream Partners LP
Schedule of Equity Method Investments [Line Items]
Net proceeds from sale of assets						$ 1.3	943.1
Investments in unconsolidated affiliates				$ 1,198.5		1,198.5			$ 1,115.4
Interest, taxes, depreciation and amortization included in earnings from equity method investments				$ 10.0	$ 8.3	25.7	15.3
Payments to Acquire Property, Plant, and Equipment						$ 134.4	$ 79.3
SWEPI LP | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Area of Land | a				100,000		100,000
Gas gathering capacity				250		250
Horsepower of compression				10,800		10,800
Payments to Acquire Property, Plant, and Equipment						$ 72.7
SWEPI LP | Crestwood Permian Basin LLC
Schedule of Equity Method Investments [Line Items]
Ownership percentage								50.00%
First Reserve Management, L.P. | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Capital commitment to acquire equity method investment	$ 151.0
Subsequent Event | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Net proceeds from sale of assets		$ 37.9
Low Pressure Gathering Lines | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Miles of pipeline | miles				194		194
High Pressure Trunklines | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Miles of pipeline | miles				36		36
High Pressure Header System [Member] | Crestwood Permian Basin Holdings
Schedule of Equity Method Investments [Line Items]
Miles of pipeline | miles				24		24