Fair Value Measurements - Breakdown by Fair Value Hierarchy Category for Financial Instruments (Details) - USD ($) $ in Millions		Sep. 30, 2022	Dec. 31, 2021
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts		$ 51.1	$ 4.5
Liabilities from commodity derivative contracts		393.9	313.1
Carrying Value [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts	[1]	230.5	46.6
Liabilities from commodity derivative contracts	[1]	560.6	363.3
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Cash and cash equivalents		192.9	158.5
Carrying Value [Member] | TRGP Revolver and Commercial Paper Program [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,182.0
Carrying Value [Member] | TRGP Senior Unsecured Notes [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		2,741.5
Carrying Value [Member] | Term Loan Facility [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,500.0
Carrying Value [Member] | Securitization Facility [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		750.0	150.0
Fair Value [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts	[1]	230.5	46.6
Liabilities from commodity derivative contracts	[1]	560.6	363.3
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Cash and cash equivalents		192.9	158.5
Fair Value [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts	[1]	0.0	0.0
Liabilities from commodity derivative contracts	[1]	0.0	0.0
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Cash and cash equivalents		0.0	0.0
Fair Value [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts	[1]	230.5	46.6
Liabilities from commodity derivative contracts	[1]	560.6	363.3
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Cash and cash equivalents		0.0	0.0
Fair Value [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Fair Value:
Assets from commodity derivative contracts	[1]	0.0	0.0
Liabilities from commodity derivative contracts	[1]	0.0	0.0
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Cash and cash equivalents		0.0	0.0
Fair Value [Member] | TRGP Revolver and Commercial Paper Program [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,182.0
Fair Value [Member] | TRGP Revolver and Commercial Paper Program [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | TRGP Revolver and Commercial Paper Program [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,182.0
Fair Value [Member] | TRGP Revolver and Commercial Paper Program [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | TRGP Senior Unsecured Notes [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		2,386.8
Fair Value [Member] | TRGP Senior Unsecured Notes [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | TRGP Senior Unsecured Notes [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		2,386.8
Fair Value [Member] | TRGP Senior Unsecured Notes [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | Term Loan Facility [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,500.0
Fair Value [Member] | Term Loan Facility [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | Term Loan Facility [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		1,500.0
Fair Value [Member] | Term Loan Facility [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0
Fair Value [Member] | Securitization Facility [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		750.0	150.0
Fair Value [Member] | Securitization Facility [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0	0.0
Fair Value [Member] | Securitization Facility [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		750.0	150.0
Fair Value [Member] | Securitization Facility [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0	0.0
Senior Unsecured Notes [Member] | Carrying Value [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		5,034.4	6,465.7
Senior Unsecured Notes [Member] | Fair Value [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		4,564.4	6,924.5
Senior Unsecured Notes [Member] | Fair Value [Member] | Level 1 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		0.0	0.0
Senior Unsecured Notes [Member] | Fair Value [Member] | Level 2 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		4,564.4	6,924.5
Senior Unsecured Notes [Member] | Fair Value [Member] | Level 3 [Member]
Financial Instruments Recorded on Our Consolidated Balance Sheets at Carrying Value:
Long-term debt		$ 0.0	$ 0.0

[1] The fair value of derivative contracts in this table is presented on a different basis than the Consolidated Balance Sheets presentation as disclosed in Note 12 – Derivative Instruments and Hedging Activities. The above fair values reflect the total value of each derivative contract taken as a whole, whereas the Consolidated Balance Sheets presentation is based on the individual maturity dates of estimated future settlements. As such, an individual contract could have both an asset and liability position when segregated into its current and long-term portions for Consolidated Balance Sheets classification purposes.