Revenues Disaggregation of Revenue (Details) $ in Millions		3 Months Ended								12 Months Ended
		Dec. 31, 2019 USD ($)	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Mar. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2019 USD ($) segments	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Disaggregation of Revenue [Line Items]
Number of Reportable Segments | segments										1
Revenues from Contracts with Customers										$ 1,266.4	$ 1,205.5
Other operating revenues	[1]									28.8	18.2
Total operating revenues		$ 327.2	$ 294.8	$ 327.3	$ 345.9	$ 325.1	$ 277.9	$ 285.3	$ 335.4	1,295.2	1,223.7	$ 1,322.6
Letter of Credit Proceeds Recognized into Transportation Revenue										26.2
Firm Service
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers	[2]									1,228.3	1,161.7
Interruptible Service
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers										29.0	32.2
Other revenues
Disaggregation of Revenue [Line Items]
Revenues from Contracts with Customers										$ 9.1	$ 11.6

[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 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 year ended December 31, 2019, contains $26.2 million of proceeds received related to the bankruptcy of a customer as discussed in Note 5.