Partners' Capital (Narrative) (Details) $ / shares in Units, $ in Millions																															1 Months Ended	9 Months Ended	12 Months Ended
	Feb. 14, 2018 USD ($) $ / shares	Feb. 07, 2018	Nov. 14, 2017 USD ($) $ / shares	Nov. 07, 2017	Aug. 14, 2017 USD ($) $ / shares	Aug. 07, 2017	May 15, 2017 USD ($) $ / shares	May 08, 2017	Feb. 14, 2017 USD ($) $ / shares	Feb. 07, 2017	Nov. 14, 2016 USD ($) $ / shares	Nov. 07, 2016	Aug. 12, 2016 USD ($) $ / shares	Aug. 05, 2016	May 13, 2016 USD ($) $ / shares	May 06, 2016	Feb. 12, 2016 USD ($) $ / shares	Feb. 05, 2016	Nov. 13, 2015 USD ($) $ / shares	Nov. 06, 2015	Sep. 30, 2015 USD ($) shares	Aug. 14, 2015 USD ($) $ / shares	Aug. 10, 2015 USD ($)	Aug. 07, 2015	May 15, 2015 USD ($) $ / shares	May 08, 2015	Feb. 13, 2015 USD ($) $ / shares	Feb. 06, 2015	Jan. 30, 2015 shares	Jun. 17, 2014 USD ($) $ / shares	Dec. 31, 2017 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($) shares	Jun. 15, 2016 shares
Distribution Made to Member or Limited Partner [Line Items]
Distribution to limited partner, distribution date			Nov. 14, 2017		Aug. 14, 2017		May 15, 2017		Feb. 14, 2017		Nov. 14, 2016		Aug. 12, 2016		May 13, 2016		Feb. 12, 2016		Nov. 13, 2015			Aug. 14, 2015			May 15, 2015		Feb. 13, 2015
Conversion ratio																					2.75											2.75
Maximum Period For Distribution Of Available Cash																																	45 days
Distribution Made to Limited Partner, Cash Distributions Paid			$ 42.2		$ 41.8		$ 41.8		$ 41.8		$ 41.4		$ 41.4		$ 41.4		$ 95.6		$ 94.3			$ 25.7			$ 25.7		$ 25.8						$ 167.6	$ 219.8	$ 171.5
Per unit rate, in dollars per unit | $ / shares			$ 0.60		$ 0.60		$ 0.60		$ 0.60		$ 0.60		$ 0.60		$ 0.60		$ 1.3750		$ 1.3750			$ 1.3750			$ 1.3750		$ 1.3750
Distributions to partners																																	(167.6)	(219.8)	(171.5)
Payments to Acquire Equity Method Investments																																	58.0	12.4	42.0
Loss on contingent consideration																																	$ (57.0)	$ 0.0	$ 0.0
Distribution made to limited partners | shares																																	4,724,030	5,815,170	1,372,573
Distributions paid to non-controlling partners																																	$ 15.2	$ 15.2	$ 234.2
Limited partners' units, issued | shares																															70,721,563		70,721,563	69,499,741
Dividends, Paid-in-kind																																	$ 43.1	$ 53.0	12.5
Common Units Available for Issuance | shares																																				7,290,552
Issuance of preferred equity of subsidiary																																	$ 0.0
Preferred units, outstanding | shares																															71,257,445		71,257,445	66,533,415
Preferred units, issued | shares																															71,257,445		71,257,445	66,533,415
Equity Offering Program Authorized Amount																																	$ 250.0
Equity Distribution Program Management Fee Percentage																																	2.00%
Payments of Stock Issuance Costs																																	$ 0.3
Distribution to limited partner, record date				Nov. 07, 2017		Aug. 07, 2017		May 08, 2017		Feb. 07, 2017		Nov. 07, 2016		Aug. 05, 2016		May 06, 2016		Feb. 05, 2016		Nov. 06, 2015				Aug. 07, 2015		May 08, 2015		Feb. 06, 2015
Payments for Repurchase of Redeemable Noncontrolling Interest																															$ 202.7		202.7	$ 0.0	0.0
Proceeds from Noncontrolling Interests																															$ 175.0		$ 175.0	0.0	0.0
Preferred Units, Class A
Distribution Made to Member or Limited Partner [Line Items]
Net proceeds from the issuance of Crestwood Midstream Partners LP Class A preferred units																							$ 58.8
Partners' Capital Account, Private Placement of Units, Price Per Unit | $ / shares																														$ 25.10			$ 9.13
Proceeds from Issuance of Preferred Limited Partners Units, Gross																							$ 60.0
Crestwood Equity Partners LP
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid																					$ 378.3											$ 378.3
Preferred units, issued | shares																					59,345,672											59,345,672
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest																																	99.90%
Crestwood Niobrara LLC | Cash distribution
Distribution Made to Member or Limited Partner [Line Items]
Distributions paid to non-controlling partners																																	$ 15.2	15.2	11.3
Crestwood Gas Services GP, LLC [Member]
Distribution Made to Member or Limited Partner [Line Items]
Limited Liability Company or Limited Partnership, Members or Limited Partners, Ownership Interest																																	0.10%
CMLP
Distribution Made to Member or Limited Partner [Line Items]
Distribution to limited partner, distribution date																						Aug. 14, 2015			May 15, 2015		Feb. 13, 2015
Net proceeds from the issuance of Crestwood Midstream Partners LP Class A preferred units																																	$ 0.0	0.0	58.8
Maximum Period For Distribution Of Available Cash																																	45 days
Distribution Made to General Partner, Cash Distributions Paid																																			31.4
Distribution Made to Limited Partner, Cash Distributions Paid																						$ 74.3			$ 74.3		$ 74.3							222.9
Dividends received from CMLP																																	$ 174.0	227.6	175.6
Per unit rate, in dollars per unit | $ / shares																						$ 0.41			$ 0.41		$ 0.41
Distributions to partners																																	(189.2)	(242.8)	(819.5)
Payments to Acquire Equity Method Investments																																	58.0	12.4	41.8
Loss on contingent consideration																																	(57.0)	0.0	$ 0.0
Distribution made to limited partners | shares																																			1,271,935
Dividends, Paid-in-kind																																			$ 31.9
Issuance of preferred equity of subsidiary																																	175.0
Preferred units, outstanding | shares																					21,580,244											21,580,244
Distribution to limited partner, record date																								Aug. 07, 2015		May 08, 2015		Feb. 06, 2015
Payments for Repurchase of Redeemable Noncontrolling Interest																																	202.7	0.0
Proceeds from Noncontrolling Interests																																	175.0	0.0	0.0
Tres Palacios Holdings LLC
Distribution Made to Member or Limited Partner [Line Items]
Payments to Acquire Equity Method Investments																																	$ 5.6	11.0	5.7
Equity method ownership percentage																															50.01%		50.01%
Tres Palacios Holdings LLC | CMLP
Distribution Made to Member or Limited Partner [Line Items]
Equity method ownership percentage																															50.01%		50.01%
Jackalope Gas Gathering Services, LLC
Distribution Made to Member or Limited Partner [Line Items]
Equity method ownership percentage																															50.00%		50.00%
Jackalope Gas Gathering Services, LLC | Preferred Units
Distribution Made to Member or Limited Partner [Line Items]
Distribution made to limited partners | shares																													3,680,570
Jackalope Gas Gathering Services, LLC | Crestwood Niobrara LLC
Distribution Made to Member or Limited Partner [Line Items]
Payments to Acquire Equity Method Investments																																	$ 3.5	$ 1.4	25.4
Cash distribution
Distribution Made to Member or Limited Partner [Line Items]
Distributions paid to non-controlling partners																																			$ 222.9
Cash distribution | Subsequent Event
Distribution Made to Member or Limited Partner [Line Items]
Distribution to limited partner, distribution date	Feb. 14, 2018
Distribution declared per limited partner unit | $ / shares	$ 0.600
Distribution to limited partner, record date		Feb. 07, 2018
Preferred Partner
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid																																	$ 15.0
Partners' Capital, Distribution Amount Per Share | $ / shares																															$ 0.2567		$ 0.2567
Partners' Capital, Contingent Distribution Amount Per Share | $ / shares																															0.2111		$ 0.2111
Partner's Capital, Unpaid Distribution, Accrual Percentage																																	2.8125%
Preferred Partner | Subsequent Event
Distribution Made to Member or Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Paid	$ 15.0
Preferred Partner | CMLP
Distribution Made to Member or Limited Partner [Line Items]
Partners' Capital, Distribution Amount Per Share | $ / shares																															$ 0.5804		$ 0.5804
Partners' Capital Account, Private Placement of Units, Price Per Unit | $ / shares																																	25.10
Subordinated Unit | Limited Partners
Distribution Made to Member or Limited Partner [Line Items]
Limited partners' units, issued | shares																																			438,789
Partners' Capital Account, Units, Cash Distribution Threshold, Quarterly Distribution | $ / shares																																	1.30
Partners' Capital Account, Units, Conversion Threshold, Cumulative Distribution | $ / shares																																	$ 5.20
Non-Controlling Partners
Distribution Made to Member or Limited Partner [Line Items]
Contribution from issuance of units																																	$ 0.0
Issuance of preferred equity of subsidiary																																	175.0
Non-Controlling Partners | CMLP
Distribution Made to Member or Limited Partner [Line Items]
Net proceeds from the issuance of Crestwood Midstream Partners LP Class A preferred units																																			$ 0.0
Issuance of preferred equity of subsidiary																																	$ 175.0
Limited Partners | CMLP
Distribution Made to Member or Limited Partner [Line Items]
Net proceeds from the issuance of Crestwood Midstream Partners LP Class A preferred units																																			$ 0.0
Maximum | Class A Purchasers | Preferred Units, Class A
Distribution Made to Member or Limited Partner [Line Items]
Contribution from issuance of units																														$ 500.0