Investments in Unconsolidated Affiliates - Activity Related to Partnership's Investments in Unconsolidated Affiliates (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period		$ 586.5
Equity earnings (loss)		5.6	$ 11.8
Balance at end of period		579.8
Targa Resources Partners LP [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period		586.5
Equity earnings (loss)		5.6
Cash Distributions		(12.8)
Contributions		0.5
Balance at end of period		579.8
Targa Resources Partners LP [Member] | GCX [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[1]	421.0
Equity earnings (loss)	[1]	5.7
Cash Distributions	[1]	(7.3)
Balance at end of period	[1]	419.4
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)		0.3
Cash Distributions		(4.7)
Balance at end of period		93.7
Targa Resources Partners LP [Member] | T2 Eagle Ford [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[2]	21.9
Equity earnings (loss)	[2]	(0.6)
Cash Distributions	[2]	(0.8)
Balance at end of period	[2]	20.5
Targa Resources Partners LP [Member] | T2 LaSalle [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[2]	4.2
Equity earnings (loss)	[2]	(0.2)
Balance at end of period	[2]	4.0
Targa Resources Partners LP [Member] | Gulf Coast Fractionators LP [Member]
Schedule Of Equity Method Investments [Line Items]
Balance at beginning of period	[3]	28.8
Equity earnings (loss)	[3]	(0.7)
Contributions	[3]	0.5
Balance at end of period	[3]	28.6
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)		1.1
Balance at end of period		$ 13.6

[1] Following the DevCo JV Repurchase in January 2022, we owned a 25% equity interest in GCX. In February 2022, we announced the GCX Sale, at which time we ceased the recognition of equity earnings (loss) due to the terms of the sales agreement. See Note 4 – Joint Ventures, Divestitures and Acquisitions for further discussion.

[2] In April 2022, we closed on the Southcross Acquisition. Following the closing of the Southcross Acquisition, we own 100% of the interests in the T2 Joint Ventures. See Note 4 – Joint Ventures, Divestitures and Acquisitions for further discussion.

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