Commitments and Contingencies (Narrative) (Details)		12 Months Ended
	Dec. 13, 2017 USD ($)	Dec. 31, 2017 USD ($) bbl Release	Dec. 31, 2016 USD ($)	Sep. 15, 2015 USD ($)	May 06, 2015 bbl
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Number of Plaintiffs		13
Accrued property taxes		$ 4,800,000	$ 4,200,000
Loss Contingency Accrual, at Carrying Value		2,100,000	100,000
Environmental Remediation Expense	$ 49,000
Estimated Environmental Costs	$ 173,000
Accrual for Environmental Loss Contingencies		1,900,000	2,100,000
Other Growth and Maintenance Contractual Purchase Obligations
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments		63,900,000
Commodity
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments		479,300,000
Crestwood Equity Partners LP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Self-insurance reserves		13,600,000	15,600,000
Self-insurance reserve expected to be paid in next fiscal year		9,100,000
CMLP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Accrued property taxes		4,800,000	4,200,000
Self-insurance reserves		11,600,000	$ 12,200,000
Self-insurance reserve expected to be paid in next fiscal year		$ 7,600,000
Maximum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Number of Plaintiffs		150
Loss Contingency, Estimate of Possible Loss		$ 3,100,000		$ 1,100,000
Minimum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Estimate of Possible Loss		$ 1,900,000
Fort Berthold Indian Reservation
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Site Contingency, Loss Exposure, Number of Releases of Produced Water | Release		3
Site Contingency, Loss Exposure, Release of Produced Water | bbl		28,000			5,200