Commitments and Contingencies (Narrative) (Details) $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2019 bbl Release	Dec. 31, 2019 USD ($) miles	Dec. 31, 2019 USD ($) miles	Dec. 31, 2014 bbl Release	Dec. 31, 2018 USD ($)	Sep. 15, 2015 USD ($)	May 31, 2015 bbl
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Damages Sought, Value			$ 55.0
Loss Contingency Accrual, at Carrying Value		$ 10.7	$ 10.7		$ 0.1
Miles of Water Gathering Pipeline Removed | miles		30	30
Asset Impairment Charges		$ 4.3
Miles of Water Gathering Pipeline Replaced | miles		12	12
Accrual for Environmental Loss Contingencies		$ 6.7	$ 6.7		1.8
Other Growth and Maintenance Contractual Purchase Obligations
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments		126.6	126.6
Commodity
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments		792.4	792.4
Purchase Obligation, Due in Next Twelve Months		712.3	712.3
Crestwood Equity Partners LP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Self-insurance reserves		9.7	9.7		11.3
Self-insurance reserve expected to be paid in next fiscal year		6.2	6.2
CMLP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Self-insurance reserves		8.3	8.3		$ 9.6
Self-insurance reserve expected to be paid in next fiscal year		5.2	5.2
Maximum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Estimate of Possible Loss		11.1	11.1			$ 1.1
Minimum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 6.7	$ 6.7
Fort Berthold Indian Reservation
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Site Contingency, Loss Exposure, Number of Releases of Produced Water | Release	2			3
Site Contingency, Loss Exposure, Release of Produced Water | bbl	5,000			28,000			5,200