Commitments and Contingencies (Narrative) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($) bbl Release	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Sep. 15, 2015 USD ($)	May. 06, 2015 bbl	Feb. 28, 2015 USD ($)	Nov. 08, 2013 bbl people
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Estimate of Possible Loss	$ 7.0
Payments for Other Taxes	8.6
Loss Contingency Accrual, at Carrying Value	0.1	$ 1.0
Loss Contingency, Range of Possible Loss, Maximum				$ 1.1
Operations and maintenance	190.2	203.3	$ 104.6
Accrual for Environmental Loss Contingencies	1.7	1.1
Identified Growth Projects
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments	12.7
Other Growth and Maintenance Contractual Purchase Obligations
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments	13.5
Commodity
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Firm Purchase Commitments	188.3
Antero
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Contingent consideration, current liability		40.0				$ 40.0
Tres Palacios Holdings LLC
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Loss Contingency, Estimate of Possible Loss	2.0
Crestwood Equity Partners LP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Self-insurance reserves	17.2	14.6
Self-insurance reserve expected to be paid in next fiscal year	11.3
CMLP
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Operations and maintenance	188.7	195.4	$ 103.4
Total current liabilities	111.6	176.3
Self-insurance reserves	11.4	$ 7.2
Self-insurance reserve expected to be paid in next fiscal year	7.1
Minimum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Accrual for Environmental Loss Contingencies	1.7
Maximum
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Accrual for Environmental Loss Contingencies	$ 3.7
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
Arrow Acquisition Class Action Lawsuit
Purchase Commitment, Excluding Long-term Commitment [Line Items]
Barrels of Oil Equivalents Spilled | bbl							50,000
Loss Contingency, Loss of Life, Number | people							47