Investments in Unconsolidated Affiliates Net Investments In and Earnings (Loss) from Unconsolidated Affiliates (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Schedule of Equity Method Investments [Line Items]
Net proceeds from sale of assets	$ 945.0			$ 1.0	$ 942.0
Proceeds from equity method investments				39.3	17.4
Investment		$ 1,181.7		1,181.7		$ 1,115.4
Earnings from unconsolidated affiliates, net		9.6	$ 6.2	17.7	12.7
Goodwill		199.0		199.0		199.0
Goodwill impairment		0.0	0.0	0.0	109.7
Stagecoach Gas Services LLC
Schedule of Equity Method Investments [Line Items]
Net proceeds from sale of assets					3.0
Proceeds from equity method investments				23.7	0.0
Investment		859.9		859.9		871.0
Earnings from unconsolidated affiliates, net		6.6	2.3	12.6	2.3
Difference between carrying amount and underlying equity		51.4		51.4
Jackalope Gas Gathering Services, L.L.C.
Schedule of Equity Method Investments [Line Items]
Proceeds from equity method investments				12.3	12.1
Investment		190.4		190.4		197.2
Earnings from unconsolidated affiliates, net		2.2	5.9	4.0	11.0
Difference between carrying amount and underlying equity		0.8		0.8
Tres Palacios Holdings LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from equity method investments				2.7	4.1
Investment		37.5		37.5		39.0
Earnings from unconsolidated affiliates, net		0.7	(2.3)	1.2	(1.5)
Difference between carrying amount and underlying equity		27.2		27.2
Powder River Basin Industrial Complex, LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from equity method investments				0.6	1.2
Investment		8.6		8.6		8.7
Earnings from unconsolidated affiliates, net		0.5	0.3	0.5	0.9
Difference between carrying amount and underlying equity		6.7		6.7
Goodwill impairment						41.3
Equity Method Investment Excess Basis Difference Adjustment						8.3
Crestwood Permian Basin Holdings LLC
Schedule of Equity Method Investments [Line Items]
Proceeds from equity method investments				0.0	0.0
Investment		85.3		85.3		$ (0.5)
Earnings from unconsolidated affiliates, net		(0.4)	$ 0.0	(0.6)	$ 0.0
Difference between carrying amount and underlying equity		$ 23.9		$ 23.9