Condensed Consolidating Financial Information (Statements Of Cash Flows) (Details) - USD ($) $ in Millions	1 Months Ended	9 Months Ended
	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities		$ 228.2	$ 244.5
Cash flows from investing activities:
Purchases of property, plant and equipment		(134.4)	(79.3)
Investment in unconsolidated affiliates		(46.5)	(6.2)
Net proceeds from sale of assets	$ 945.0	1.3	943.1
Proceeds from Equity Method Investment, Distribution, Return of Capital		35.3	9.2
Net cash used in investing activities		(144.3)	866.8
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,209.8	1,364.0
Payments on long-term debt		(2,159.2)	(2,279.4)
Payments on capital leases		(2.2)	(1.5)
Payments for debt-related deferred costs		(1.0)	(3.4)
Distributions to partners		(125.4)	(178.4)
Taxes paid for unit-based compensation vesting		(5.3)	(0.8)
Other		0.0	0.1
Net cash provided by (used in) financing activities		(84.1)	(1,110.8)
Net change in cash		(0.2)	0.5
Cash at beginning of period		1.6	0.5
Cash at end of period		1.4	1.0
Eliminations
Cash flows from operating activities		0.0	0.0
Cash flows from investing activities:
Purchases of property, plant and equipment		0.0	0.0
Investment in unconsolidated affiliates		0.0	0.0
Net proceeds from sale of assets		0.0	0.0
Capital distributions from consolidated affiliates		(0.9)	(11.5)
Proceeds from Equity Method Investment, Distribution, Return of Capital		0.0	0.0
Net cash used in investing activities		(0.9)	(11.5)
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0
Payments on long-term debt		0.0	0.0
Payments on capital leases		0.0	0.0
Payments for debt-related deferred costs		0.0	0.0
Distributions to partners		0.0	0.0
Contributions from (distributions to) parent		0.9	11.5
Taxes paid for unit-based compensation vesting		0.0	0.0
Change in intercompany balances		0.0	0.0
Other			0.0
Net cash provided by (used in) financing activities		0.9	11.5
Net change in cash		0.0	0.0
Cash at beginning of period		0.0	0.0
Cash at end of period		0.0	0.0
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities		23.5	19.9
Cash flows from investing activities:
Purchases of property, plant and equipment		0.0	0.0
Investment in unconsolidated affiliates		(46.5)	(6.2)
Net proceeds from sale of assets		0.0	0.0
Capital distributions from consolidated affiliates		0.0	0.0
Proceeds from Equity Method Investment, Distribution, Return of Capital		35.3	9.2
Net cash used in investing activities		(11.2)	3.0
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0
Payments on long-term debt		0.0	0.0
Payments on capital leases		0.0	0.0
Payments for debt-related deferred costs		0.0	0.0
Distributions to partners		(11.4)	(11.4)
Contributions from (distributions to) parent		(0.9)	(11.5)
Taxes paid for unit-based compensation vesting		0.0	0.0
Change in intercompany balances		0.0	0.0
Other			0.0
Net cash provided by (used in) financing activities		(12.3)	(22.9)
Net change in cash		0.0	0.0
Cash at beginning of period		0.0	0.0
Cash at end of period		0.0	0.0
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Cash flows from operating activities		(102.6)	(140.4)
Cash flows from investing activities:
Purchases of property, plant and equipment		(5.8)	(1.6)
Investment in unconsolidated affiliates		0.0	0.0
Net proceeds from sale of assets		0.0	0.0
Capital distributions from consolidated affiliates		0.9	11.5
Proceeds from Equity Method Investment, Distribution, Return of Capital		0.0	0.0
Net cash used in investing activities		(4.9)	9.9
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,209.8	1,364.0
Payments on long-term debt		(2,157.9)	(2,278.4)
Payments on capital leases		0.0	0.0
Payments for debt-related deferred costs		(1.0)	(3.4)
Distributions to partners		(119.5)	(185.0)
Contributions from (distributions to) parent		0.0	0.0
Taxes paid for unit-based compensation vesting		0.0	0.0
Change in intercompany balances		175.9	1,233.7
Other			0.0
Net cash provided by (used in) financing activities		107.3	130.9
Net change in cash		(0.2)	0.4
Cash at beginning of period		1.3	0.1
Cash at end of period		1.1	0.5
Crestwood Midstream Partners LP
Cash flows from operating activities		232.9	250.8
Cash flows from investing activities:
Purchases of property, plant and equipment		(134.4)	(79.3)
Investment in unconsolidated affiliates		(46.5)	(6.2)
Net proceeds from sale of assets		1.3	943.1
Capital distributions from consolidated affiliates		0.0	0.0
Proceeds from Equity Method Investment, Distribution, Return of Capital		35.3	9.2
Net cash used in investing activities		(144.3)	866.8
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,209.8	1,364.0
Payments on long-term debt		(2,159.2)	(2,279.2)
Payments on capital leases		(2.2)	(1.5)
Payments for debt-related deferred costs		(1.0)	(3.4)
Distributions to partners		(130.9)	(196.4)
Contributions from (distributions to) parent		0.0	0.0
Taxes paid for unit-based compensation vesting		(5.3)	(0.8)
Change in intercompany balances		0.0	0.0
Other			0.1
Net cash provided by (used in) financing activities		(88.8)	(1,117.2)
Net change in cash		(0.2)	0.4
Cash at beginning of period		1.3	0.1
Cash at end of period		1.1	0.5
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities		312.0	371.3
Cash flows from investing activities:
Purchases of property, plant and equipment		(128.6)	(77.7)
Investment in unconsolidated affiliates		0.0	0.0
Net proceeds from sale of assets		1.3	943.1
Capital distributions from consolidated affiliates		0.0	0.0
Proceeds from Equity Method Investment, Distribution, Return of Capital		0.0	0.0
Net cash used in investing activities		(127.3)	865.4
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0
Payments on long-term debt		(1.3)	(0.8)
Payments on capital leases		(2.2)	(1.5)
Payments for debt-related deferred costs		0.0	0.0
Distributions to partners		0.0	0.0
Contributions from (distributions to) parent		0.0	0.0
Taxes paid for unit-based compensation vesting		(5.3)	(0.8)
Change in intercompany balances		(175.9)	(1,233.7)
Other			0.1
Net cash provided by (used in) financing activities		(184.7)	(1,236.7)
Net change in cash		0.0	0.0
Cash at beginning of period		0.0	0.0
Cash at end of period		$ 0.0	$ 0.0