Segment Information - Other Financial Information (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Dec. 31, 2020
Other financial information [Abstract]
Total assets		$ 15,972.7		$ 15,972.7		$ 15,875.7
Operating Segments [Member]
Other financial information [Abstract]
Total assets	[1]	15,972.7	$ 16,052.1	15,972.7	$ 16,052.1
Goodwill		45.2	45.2	45.2	45.2
Capital expenditures		117.5	136.6	316.5	610.3
Operating Segments [Member] | Gathering and Processing [Member]
Other financial information [Abstract]
Total assets	[1]	8,560.6	8,929.4	8,560.6	8,929.4
Goodwill		45.2	45.2	45.2	45.2
Capital expenditures		98.0	63.6	265.4	218.0
Operating Segments [Member] | Logistics And Transportation [Member]
Other financial information [Abstract]
Total assets	[1]	7,180.5	6,841.2	7,180.5	6,841.2
Capital expenditures		16.8	69.0	42.0	375.5
Operating Segments [Member] | Other [Member]
Other financial information [Abstract]
Total assets	[1]	42.3	78.2	42.3	78.2
Operating Segments [Member] | Corporate and Eliminations [Member]
Other financial information [Abstract]
Total assets	[1]	189.3	203.3	189.3	203.3
Capital expenditures		$ 2.7	$ 4.0	$ 9.1	$ 16.8

[1] Assets in the Corporate and Eliminations column primarily include tax-related assets, cash, prepaids and debt issuance costs for our revolving credit facilities.