Hedging Activities and Fair Value Measurements (Details) bbl in Millions, $ in Millions, ft³ in Billions		12 Months Ended
		Dec. 31, 2020 USD ($) Contract bbl ft³	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Derivative [Line Items]
Payments for the settlement of interest rate derivative instruments | $		$ (33.3)	$ 0.0	$ 22.1
Gain on the sale of swaption | $			23.1	29.4
Carrying amount of hedged asset | $		144.0	$ 31.7
Forward Starting Swaps [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Notional Amount | $		$ 1,080.0
Weighted-Average Rate Locked		1.83%
Life of associated future debt		30 years
Notional amount of settled derivative instruments | $		$ 575.0		275.0
Payments for the settlement of interest rate derivative instruments | $		$ (33.3)		$ 22.1
Forward Starting Swaps - May 2019 [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract		1
Notional Amount | $		$ 75.0
Weighted-Average Rate Locked		2.41%
Forward Starting Swaps - September 2019 [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract		10
Notional Amount | $		$ 1,000.0
Forward Starting Swaps D [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract		5
Notional Amount | $		$ 500.0
Weighted-Average Rate Locked		2.13%
Forward Starting Swaps - January 2020 [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract	[1]	2
Notional Amount | $		$ 150.0
Weighted-Average Rate Locked		1.72%
Forward Starting Swaps - February 2020 (A) [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract	[1]	1
Notional Amount | $		$ 100.0
Weighted-Average Rate Locked		1.46%
Forward Starting Swaps - February 2020 (B) [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract	[1]	2
Notional Amount | $		$ 150.0
Weighted-Average Rate Locked		1.48%
Forward Starting Swaps - March 2020 [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract	[1]	2
Notional Amount | $		$ 100.0
Weighted-Average Rate Locked		0.95%
Designated as Hedging Instrument [Member] | Natural gas processing: Forecasted natural gas purchases for plant thermal reduction (PTR) [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume | ft³	[2],[3]	6.0
Designated as Hedging Instrument [Member] | Natural gas processing: Forecasted sales of NGLs [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	0.6
Designated as Hedging Instrument [Member] | Natural gas marketing: Natural gas storage inventory management activities [Member] | Derivatives in fair value hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume | ft³	[2],[3]	4.0
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted purchases of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	142.8
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted purchases of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume	[2],[3]	1.6
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted sales of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	172.1
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted sales of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume	[2],[3]	4.5
Designated as Hedging Instrument [Member] | NGL marketing: NGLs inventory management activities [Member] | Derivatives in fair value hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	1.9
Designated as Hedging Instrument [Member] | Refined products marketing: Forecasted purchases of refined products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	41.2
Designated as Hedging Instrument [Member] | Refined products marketing: Forecasted sales of refined products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	51.1
Designated as Hedging Instrument [Member] | Refined products marketing: Forecasted sales of refined products [Member] | Derivatives in cash flow hedging relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume	[2],[3]	3.3
Designated as Hedging Instrument [Member] | Refined products marketing: Refined products inventory management activities [Member] | Derivatives in fair value hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	0.8
Designated as Hedging Instrument [Member] | Crude oil marketing: Forecasted purchases of crude oil [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	32.9
Designated as Hedging Instrument [Member] | Crude oil marketing: Forecasted sales of crude oil [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	44.5
Designated as Hedging Instrument [Member] | Petrochemical marketing: Forecasted purchases of petrochemical products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	0.4
Designated as Hedging Instrument [Member] | Petrochemical marketing: Forecasted sales of petrochemical products [Member] | Derivatives in cash flow hedging relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3]	0.5
Not Designated as Hedging Instrument [Member] | Natural gas risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Current [Member]
Derivative [Line Items]
Volume | ft³	[2],[3],[4]	10.3
Not Designated as Hedging Instrument [Member] | Natural gas risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume | ft³	[2],[3],[4]	0.4
Not Designated as Hedging Instrument [Member] | NGL risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3],[4]	26.5
Not Designated as Hedging Instrument [Member] | NGL risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume	[2],[3],[4]	7.9
Not Designated as Hedging Instrument [Member] | Refined products risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3],[4]	6.9
Not Designated as Hedging Instrument [Member] | Crude oil risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Current [Member]
Derivative [Line Items]
Volume	[2],[3],[4]	32.5
Not Designated as Hedging Instrument [Member] | Crude oil risk management activities [Member] | Derivatives in mark-to-market relationships [Member] | Long-term [Member]
Derivative [Line Items]
Volume	[2],[3],[4]	2.6

[1] These swaps were entered into during the first quarter of 2020.

[2] The maximum term for derivatives designated as cash flow hedges, derivatives designated as fair value hedges and derivatives not designated as hedging instruments is December 2022, December 2021 and October 2023, respectively.

[3] Volume for derivatives designated as hedging instruments reflects the total amount of volumes hedged whereas volume for derivatives not designated as hedging instruments reflects the absolute value of derivative notional volumes.

[4] Reflects the use of derivative instruments to manage risks associated with transportation, processing and storage assets.