Reportable Segments (Details) $ in Millions	3 Months Ended
	Mar. 31, 2025 USD ($) segments	Mar. 31, 2024 USD ($)	Dec. 31, 2024 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | segments	2
Operating Revenues	$ 618.6	$ 510.5
Costs associated with service revenues	8.0	7.2
Costs associated with product sales	122.9	63.8
Operation and maintenance	58.2	58.9
Administrative and general	48.3	49.3
Taxes other than income taxes	32.3	31.7
Gain on sale of assets, impairments and other	(1.0)	(7.7)
Miscellaneous other income, net	1.2	3.0
Segment EBITDA	351.1	310.3
Depreciation and amortization	105.5	105.5
Interest expense	39.5	43.3
Interest income	(1.0)	(3.7)
Consolidated income before income taxes	207.1	165.2
Total Assets	9,849.6		$ 9,779.4
Capital expenditures	51.6	97.3
Operating Segments
Segment Reporting Information [Line Items]
Revenue From External Customers	618.6	510.5
Intrasegment revenues	13.0	12.4
Operating Revenues	631.6	522.9
Total Assets	9,057.9		9,118.8
Intersegment Eliminations
Segment Reporting Information [Line Items]
Intrasegment revenues	13.0	12.4
Operating Revenues	(13.0)	(12.4)
Natural Gas Reportable Segment
Segment Reporting Information [Line Items]
Revenue From External Customers	410.7	373.3
Natural Gas Reportable Segment | Operating Segments
Segment Reporting Information [Line Items]
Intrasegment revenues	13.0	12.4
Operating Revenues	423.7	385.7
Costs associated with service revenues	12.0	10.0
Costs associated with product sales	0.0	0.0
Operation and maintenance	47.8	46.5
Administrative and general	46.5	47.2
Taxes other than income taxes	28.9	28.3
Gain on sale of assets, impairments and other	(1.0)	(7.7)
Miscellaneous other income, net	(1.1)	(2.9)
Segment EBITDA	290.6	264.3
Total Assets	7,547.0		7,490.1
Capital expenditures	42.8	79.0
Natural Gas Liquids Reportable Segment
Segment Reporting Information [Line Items]
Revenue From External Customers	207.9	137.2
Natural Gas Liquids Reportable Segment | Operating Segments
Segment Reporting Information [Line Items]
Operating Revenues	207.9	137.2
Costs associated with service revenues	4.3	4.7
Costs associated with product sales	122.9	63.8
Operation and maintenance	10.4	12.4
Administrative and general	6.5	7.0
Taxes other than income taxes	3.4	3.4
Gain on sale of assets, impairments and other	0.0	0.0
Miscellaneous other income, net	(0.1)	(0.1)
Segment EBITDA	60.5	46.0
Total Assets	1,510.9		$ 1,628.7
Capital expenditures	$ 8.8	$ 18.3