Condensed Consolidating Financial Information (Statements Of Cash Flows) (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities		$ 420.4	$ 253.6	$ 255.9
Cash flows from investing activities:
Acquisition, net of cash acquired		(462.1)	0.0	0.0
Purchases of property, plant and equipment		(455.5)	(305.5)	(188.4)
Investment in unconsolidated affiliates		(61.3)	(64.4)	(58.0)
Net proceeds from sale of assets		0.8	79.5	225.2
Other		(1.1)	0.0	0.0
Capital distributions from unconsolidated affiliates		35.5	49.2	59.9
Net cash provided by (used in) investing activities		(943.7)	(241.2)	38.7
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,307.3	2,274.8	2,838.6
Payments on long-term debt		(1,729.5)	(2,015.7)	(2,913.9)
Payments on finance leases		3.5
Payments on capital leases			(1.6)	(2.7)
Payments for deferred financing costs		(9.0)	(5.7)	(1.0)
Redemption of non-controlling interest	$ (202.7)	0.0	0.0	(202.7)
Distributions to partners		(172.4)	(170.8)	(167.6)
Net proceeds from issuance of non-controlling interest	175.0	235.0	0.0	175.0
Taxes paid for unit-based compensation vesting		(11.0)	(7.4)	(5.5)
Other		0.0	(0.1)	(0.1)
Net cash provided by (used in) financing activities		531.8	3.5	(294.9)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		8.5	15.9	(0.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1.3	25.7	17.2	1.3	$ 1.6
Eliminations
Cash flows from operating activities		0.0	0.0	0.0
Cash flows from investing activities:
Acquisition, net of cash acquired		0.0
Purchases of property, plant and equipment		0.0	0.0	0.0
Investment in unconsolidated affiliates		0.0	0.0	0.0
Net proceeds from sale of assets		0.0	0.0	0.0
Other		0.0
Capital distributions from unconsolidated affiliates		0.0	0.0	0.0
Capital contributions to consolidated affiliates		203.8	(27.9)	(4.3)
Net cash provided by (used in) investing activities		203.8	(27.9)	(4.3)
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0	0.0
Payments on long-term debt		0.0	0.0	0.0
Payments on finance leases		0.0
Payments on capital leases			0.0	0.0
Payments for deferred financing costs		0.0	0.0	0.0
Redemption of non-controlling interest				0.0
Distributions to partners		0.0	0.0	0.0
Distributions to partners		(203.8)	27.9	4.3
Net proceeds from issuance of non-controlling interest		0.0		0.0
Taxes paid for unit-based compensation vesting		0.0	0.0	0.0
Change in intercompany balances		0.0	0.0	0.0
Other			0.0	0.0
Net cash provided by (used in) financing activities		(203.8)	27.9	4.3
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		0.0	0.0	0.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.0	0.0	0.0	0.0	0.0
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Cash flows from operating activities		(171.0)	(131.7)	(162.3)
Cash flows from investing activities:
Acquisition, net of cash acquired		0.0
Purchases of property, plant and equipment		0.0	0.0	0.0
Investment in unconsolidated affiliates		0.0	0.0	0.0
Net proceeds from sale of assets		0.0	0.0	0.0
Other		0.0
Capital distributions from unconsolidated affiliates		0.0	0.0	0.0
Capital contributions to consolidated affiliates		(203.8)	27.9	4.3
Net cash provided by (used in) investing activities		(203.8)	27.9	4.3
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,307.3	2,274.8	2,838.6
Payments on long-term debt		(1,728.6)	(2,014.8)	(2,912.6)
Payments on finance leases		0.0
Payments on capital leases			0.0	0.0
Payments for deferred financing costs		(9.0)	(5.7)	(1.0)
Redemption of non-controlling interest				0.0
Distributions to partners		(235.8)	(238.4)	(174.0)
Distributions to partners		0.0	0.0	0.0
Net proceeds from issuance of non-controlling interest		0.0		0.0
Taxes paid for unit-based compensation vesting		0.0	0.0	0.0
Change in intercompany balances		26.2	103.4	406.7
Other			0.0	0.0
Net cash provided by (used in) financing activities		360.1	119.3	157.7
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(14.7)	15.5	(0.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1.0	1.8	16.5	1.0	1.3
CMLP
Cash flows from operating activities		424.1	260.5	262.2
Cash flows from investing activities:
Acquisition, net of cash acquired		(462.1)
Purchases of property, plant and equipment		(455.5)	(305.5)	(188.4)
Investment in unconsolidated affiliates		(61.3)	(64.4)	(58.0)
Net proceeds from sale of assets		0.8	79.5	225.2
Other		(1.1)
Capital distributions from unconsolidated affiliates		35.5	49.2	59.9
Capital contributions to consolidated affiliates		0.0	0.0	0.0
Net cash provided by (used in) investing activities		(943.7)	(241.2)	38.7
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,307.3	2,274.8	2,838.6
Payments on long-term debt		(1,729.5)	(2,015.7)	(2,913.9)
Payments on finance leases		3.5
Payments on capital leases			(1.6)	(2.7)
Payments for deferred financing costs		(9.0)	(5.7)	(1.0)
Redemption of non-controlling interest				(202.7)
Distributions to partners		(260.8)	(248.3)	(189.2)
Distributions to partners		0.0	0.0	0.0
Net proceeds from issuance of non-controlling interest		235.0		175.0
Taxes paid for unit-based compensation vesting		(11.0)	(7.4)	(5.5)
Change in intercompany balances		0.0	0.0	0.0
Other			0.1	0.2
Net cash provided by (used in) financing activities		528.5	(3.8)	(301.2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		8.9	15.5	(0.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1.0	25.4	16.5	1.0	1.3
Non-Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities		126.0	53.0	45.3
Cash flows from investing activities:
Acquisition, net of cash acquired		(462.1)
Purchases of property, plant and equipment		(197.4)	0.0	0.0
Investment in unconsolidated affiliates		(61.3)	(64.4)	(58.0)
Net proceeds from sale of assets		0.0	0.0	0.0
Other		0.0
Capital distributions from unconsolidated affiliates		35.5	49.2	59.9
Capital contributions to consolidated affiliates		0.0	0.0	0.0
Net cash provided by (used in) investing activities		(685.3)	(15.2)	1.9
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0	0.0
Payments on long-term debt		0.0	0.0	0.0
Payments on finance leases		0.0
Payments on capital leases			0.0	0.0
Payments for deferred financing costs		0.0	0.0	0.0
Redemption of non-controlling interest				(202.7)
Distributions to partners		(25.0)	(9.9)	(15.2)
Distributions to partners		203.8	(27.9)	(4.3)
Net proceeds from issuance of non-controlling interest		235.0		175.0
Taxes paid for unit-based compensation vesting		0.0	0.0	0.0
Change in intercompany balances		169.1	0.0	0.0
Other			0.0	0.0
Net cash provided by (used in) financing activities		582.9	(37.8)	(47.2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		23.6	0.0	0.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.0	23.6	0.0	0.0	0.0
Guarantor Subsidiaries | Reportable Legal Entities
Cash flows from operating activities		469.1	339.2	379.2
Cash flows from investing activities:
Acquisition, net of cash acquired		0.0
Purchases of property, plant and equipment		(258.1)	(305.5)	(188.4)
Investment in unconsolidated affiliates		0.0	0.0	0.0
Net proceeds from sale of assets		0.8	79.5	225.2
Other		(1.1)
Capital distributions from unconsolidated affiliates		0.0	0.0	0.0
Capital contributions to consolidated affiliates		0.0	0.0	0.0
Net cash provided by (used in) investing activities		(258.4)	(226.0)	36.8
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		0.0	0.0	0.0
Payments on long-term debt		(0.9)	(0.9)	(1.3)
Payments on finance leases		3.5
Payments on capital leases			(1.6)	(2.7)
Payments for deferred financing costs		0.0	0.0	0.0
Redemption of non-controlling interest				0.0
Distributions to partners		0.0	0.0	0.0
Distributions to partners		0.0	0.0	0.0
Net proceeds from issuance of non-controlling interest		0.0		0.0
Taxes paid for unit-based compensation vesting		(11.0)	(7.4)	(5.5)
Change in intercompany balances		(195.3)	(103.4)	(406.7)
Other			0.1	0.2
Net cash provided by (used in) financing activities		(210.7)	(113.2)	(416.0)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		0.0	0.0	0.0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	0.0	0.0	0.0	0.0	0.0
CMLP
Cash flows from operating activities		424.1	260.5	262.2
Cash flows from investing activities:
Acquisition, net of cash acquired		(462.1)	0.0	0.0
Purchases of property, plant and equipment		(455.5)	(305.5)	(188.4)
Investment in unconsolidated affiliates		(61.3)	(64.4)	(58.0)
Net proceeds from sale of assets		0.8	79.5	225.2
Other		(1.1)	0.0	0.0
Capital distributions from unconsolidated affiliates		35.5	49.2	59.9
Net cash provided by (used in) investing activities		(943.7)	(241.2)	38.7
Cash flows from financing activities:
Proceeds from the issuance of long-term debt		2,307.3	2,274.8	2,838.6
Payments on long-term debt		(1,729.5)	(2,015.7)	(2,913.9)
Payments on finance leases		3.5
Payments on capital leases			(1.6)	(2.7)
Payments for deferred financing costs		(9.0)	(5.7)	(1.0)
Redemption of non-controlling interest		0.0	0.0	(202.7)
Distributions to partners		(235.8)	(238.4)	(174.0)
Net proceeds from issuance of non-controlling interest		235.0	0.0	175.0
Taxes paid for unit-based compensation vesting		(11.0)	(7.4)	(5.5)
Other		0.0	0.1	0.2
Net cash provided by (used in) financing activities		528.5	(3.8)	(301.2)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		8.9	15.5	(0.3)
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	$ 1.0	$ 25.4	$ 16.5	$ 1.0	$ 1.3