Revenues Disaggregation of Revenue (Details) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2019 USD ($) segments	Jun. 30, 2018 USD ($)
Disaggregation of Revenue [Line Items]
Number of Reportable Segments | segments				1
Revenues from Contracts with Customers		$ 320.7	$ 281.1	$ 660.2	$ 612.2
Other operating revenues	[1]	6.6	4.2	13.0	8.5
Total operating revenues		327.3	285.3	673.2	620.7
Letter of Credit Proceeds Recognized into Transportation Revenue				26.2
Firm Service
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	[2]	315.1	267.5	643.9	586.4
Interruptible Service
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers		5.4	7.8	11.2	17.3
Other revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers		$ 0.2	$ 5.8	$ 5.1	$ 8.5

[1] Other operating revenues include certain revenues earned from operating leases, pipeline management fees and other activities that are not considered central and ongoing major business operations of the Company and do not represent revenues earned from contracts with customers.

[2] Revenues earned from contracts with minimum volume commitments (MVCs) are included in firm service given the stand-ready nature of the performance obligation and the guaranteed nature of the fees over the contract term. The three and six months ended June 30, 2019, contain $26.2 million of proceeds received related to the bankruptcy of a customer as discussed in Note 7.