Condensed Consolidating Financial Information (Statements Of Operations) (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues:
Revenues		$ 3,654.1	$ 3,880.9	$ 2,520.5
Related party (Note 16)		1.0	1.8	2.6
Costs of product/services sold (exclusive of items shown separately below):
Product costs - related party (Note 16)		134.7	15.3	17.7
Total costs of products/services sold		3,129.4	3,374.7	1,925.1
Operating expenses and other:
Operations and maintenance		125.8	136.0	158.1
General and administrative		88.1	96.5	88.2
Depreciation, amortization and accretion		168.7	191.7	229.6
Loss on long-lived assets, net		28.6	65.6	65.6
Goodwill impairment		0.0	38.8	162.6
Loss on contingent consideration		0.0	57.0	0.0
Total expenses		411.2	585.6	704.1
Operating income (loss)		113.5	(79.4)	(108.7)
Other income (expense):
Earnings from unconsolidated affiliates, net		53.3	47.8	31.5
Interest and debt expense, net		(99.2)	(99.4)	(125.1)
Gain (loss) on modification/extinguishment of debt	$ 10.0	(0.9)	(37.7)	10.0
Other income, net		0.4	1.3	0.5
Loss before income taxes		67.1	(167.4)	(191.8)
(Provision) benefit for income taxes		(0.1)	0.8	(0.3)
Net income (loss)		67.0	(166.6)	(192.1)
Net income attributable to non-controlling partners in subsidiary		16.2	25.3	24.2
Net income (loss) attributable to parent		50.8	(191.9)	(216.3)
Net income attributable to preferred units		60.1	62.5	28.7
Net income (loss) attributable to partners		(9.3)	(254.4)	(245.0)
Eliminations
Revenues:
Revenues		0.0	0.0	0.0
Costs of product/services sold (exclusive of items shown separately below):
Total costs of products/services sold		0.0	0.0	0.0
Operating expenses and other:
Operations and maintenance		0.0	0.0	0.0
General and administrative		0.0	0.0	0.0
Depreciation, amortization and accretion		0.0	0.0	0.0
Loss on long-lived assets, net		0.0	0.0	0.0
Goodwill impairment			0.0	0.0
Loss on contingent consideration			0.0
Total expenses		0.0	0.0	0.0
Operating income (loss)		0.0	0.0	0.0
Other income (expense):
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0
Interest and debt expense, net		0.0	0.0	0.0
Gain (loss) on modification/extinguishment of debt		0.0	0.0	0.0
Other income, net			0.0
Loss from unconsolidated affiliates		(197.6)	(3.9)	40.2
Net income (loss)		(197.6)	(3.9)	40.2
Net income attributable to non-controlling partners in subsidiary		0.0	0.0	0.0
Net income (loss) attributable to parent		(197.6)	(3.9)
Net income (loss) attributable to partners				40.2
Parent Company, Crestwood Midstream Partners, LP | Reportable Legal Entities
Revenues:
Revenues		0.0	0.0	0.0
Costs of product/services sold (exclusive of items shown separately below):
Total costs of products/services sold		0.0	0.0	0.0
Operating expenses and other:
Operations and maintenance		0.0	0.0	0.0
General and administrative		55.1	67.6	66.4
Depreciation, amortization and accretion		0.0	0.0	0.0
Loss on long-lived assets, net		0.0	0.0	0.0
Goodwill impairment			0.0	0.0
Loss on contingent consideration			0.0
Total expenses		55.1	67.6	66.4
Operating income (loss)		(55.1)	(67.6)	(66.4)
Other income (expense):
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0
Interest and debt expense, net		(99.2)	(99.4)	(125.1)
Gain (loss) on modification/extinguishment of debt		(0.9)	(37.7)	10.0
Other income, net			0.0
Loss from unconsolidated affiliates		197.6	3.9	(40.2)
Net income (loss)		42.4	(200.8)	(221.7)
Net income attributable to non-controlling partners in subsidiary		0.0	0.0	0.0
Net income (loss) attributable to parent		42.4	(200.8)
Net income (loss) attributable to partners				(221.7)
Guarantor Subsidiaries | Reportable Legal Entities
Revenues:
Revenues		3,654.1	3,880.9	2,520.5
Costs of product/services sold (exclusive of items shown separately below):
Total costs of products/services sold		3,129.4	3,374.7	1,925.1
Operating expenses and other:
Operations and maintenance		125.8	136.0	155.0
General and administrative		28.4	25.5	19.2
Depreciation, amortization and accretion		181.4	202.7	240.5
Loss on long-lived assets, net		28.6	65.6	65.6
Goodwill impairment			38.8	162.6
Loss on contingent consideration			0.0
Total expenses		364.2	468.6	642.9
Operating income (loss)		160.5	37.6	(47.5)
Other income (expense):
Earnings from unconsolidated affiliates, net		0.0	0.0	0.0
Interest and debt expense, net		0.0	0.0	0.0
Gain (loss) on modification/extinguishment of debt		0.0	0.0	0.0
Other income, net			0.8
Loss from unconsolidated affiliates		0.0	0.0	0.0
Net income (loss)		160.5	38.4	(47.5)
Net income attributable to non-controlling partners in subsidiary		0.0	0.0	0.0
Net income (loss) attributable to parent		160.5	38.4
Net income (loss) attributable to partners				(47.5)
Non-Guarantor Subsidiaries | Reportable Legal Entities
Revenues:
Revenues		0.0	0.0	0.0
Costs of product/services sold (exclusive of items shown separately below):
Total costs of products/services sold		0.0	0.0	0.0
Operating expenses and other:
Operations and maintenance		0.0	0.0	0.0
General and administrative		0.0	0.0	0.0
Depreciation, amortization and accretion		0.0	0.0	0.0
Loss on long-lived assets, net		0.0	0.0	0.0
Goodwill impairment			0.0	0.0
Loss on contingent consideration			57.0
Total expenses		0.0	57.0	0.0
Operating income (loss)		0.0	(57.0)	0.0
Other income (expense):
Earnings from unconsolidated affiliates, net		53.3	47.8	31.5
Interest and debt expense, net		0.0	0.0	0.0
Gain (loss) on modification/extinguishment of debt		0.0	0.0	0.0
Other income, net			0.0
Loss from unconsolidated affiliates		0.0	0.0	0.0
Net income (loss)		53.3	(9.2)	31.5
Net income attributable to non-controlling partners in subsidiary		16.2	25.3	24.2
Net income (loss) attributable to parent		37.1	(34.5)
Net income (loss) attributable to partners				7.3
CMLP
Revenues:
Revenues		3,654.1	3,880.9	2,520.5
Costs of product/services sold (exclusive of items shown separately below):
Total costs of products/services sold		3,129.4	3,374.7	1,925.1
Operating expenses and other:
Operations and maintenance		125.8	136.0	155.0
General and administrative		83.5	93.1	85.6
Depreciation, amortization and accretion		181.4	202.7	240.5
Loss on long-lived assets, net		28.6	65.6	65.6
Goodwill impairment			38.8	162.6
Loss on contingent consideration			57.0
Total expenses		419.3	593.2	709.3
Operating income (loss)		105.4	(87.0)	(113.9)
Other income (expense):
Earnings from unconsolidated affiliates, net		53.3	47.8	31.5
Interest and debt expense, net		(99.2)	(99.4)	(125.1)
Gain (loss) on modification/extinguishment of debt		(0.9)	(37.7)	10.0
Other income, net			0.8
Loss from unconsolidated affiliates		0.0	0.0	0.0
Net income (loss)		58.6	(175.5)	(197.5)
Net income attributable to non-controlling partners in subsidiary		16.2	25.3	24.2
Net income (loss) attributable to parent		$ 42.4	$ (200.8)
Net income (loss) attributable to partners				$ (221.7)