Partnership Units and Related Matters - Distributions (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Distributions declared and/or paid by the Partnership [Abstract]
Date Paid or To be Paid	Aug. 13, 2020	May 13, 2020	Feb. 13, 2020
Total Distributions	$ 53.1			$ 437.8	$ 295.0	$ 679.1
Distributions Paid [Member]
Distributions declared and/or paid by the Partnership [Abstract]
Total Distributions	51.7	$ 53.1	$ 241.9
Distributions to Targa Resources Corp.	$ 48.9	$ 50.3	$ 239.1