Investments in Unconsolidated Affiliates - Activity Related to Partnership's Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period				$ 586.5
Equity earnings (loss)		$ 1.7	$ 14.3	8.7	$ 38.9
Balance at end of period		136.4		136.4
Targa Resources Partners LP [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period				586.5
Equity earnings (loss)				8.7
Cash Distributions				(23.5)
Disposition/ Consolidation				436.8
Contributions				1.5
Balance at end of period		136.4		136.4
Targa Resources Partners LP [Member] | GCX [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period				421.0
Equity earnings (loss)				5.7
Cash Distributions				(14.3)
Disposition/ Consolidation				(412.4)
Targa Resources Partners LP [Member] | Little Missouri 4 [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period				98.1
Equity earnings (loss)				4.3
Cash Distributions				(7.4)
Balance at end of period		95.0		95.0
Targa Resources Partners LP [Member] | T2 Eagle Ford
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[1]			21.9
Equity earnings (loss)	[1]			(0.6)
Cash Distributions	[1]			(0.8)
Disposition/ Consolidation	[1]			(20.5)
Targa Resources Partners LP [Member] | T2 La Salle
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[1]			4.2
Equity earnings (loss)	[1]			(0.3)
Disposition/ Consolidation	[1]			(3.9)
Targa Resources Partners LP [Member] | Gulf Coast Fractionators LP [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[2]			28.8
Equity earnings (loss)	[2]			(2.4)
Contributions	[2]			1.5
Balance at end of period	[2]	27.9		27.9
Targa Resources Partners LP [Member] | Cayenne Joint Venture [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period				12.5
Equity earnings (loss)				2.0
Cash Distributions				(1.0)
Balance at end of period		$ 13.5		$ 13.5

[1] Following the closing of the South Texas Acquisition in April 2022, the T2 Joint Ventures are 100% owned and consolidated by Targa.

[2] Targa assumed operatorship of GCF in the first half of 2021.