Derivative Instruments, Hedging Activities and Fair Value Measurements (Details) bbl in Millions, $ in Millions, ft³ in Billions	3 Months Ended
	Mar. 31, 2016 USD ($) Contract bbl ft³
Interest rate derivatives [Member] | Derivatives in fair value hedging relationships [Member] | EPO Senior Notes OO [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract	10
Type of Derivatives Outstanding	fixed-to-floating swaps
Notional Amount | $	$ 750.0
Period of Hedge	5/2015 to 5/2018
Rate Swap, fixed rate (in hundredths)	1.65%
Rate Swap, floating rate (in hundredths)	1.10%
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Natural gas processing: Forecasted natural gas purchases for plant thermal reduction (PTR) [Member]
Derivative [Line Items]
Current Volume | ft³	32.7	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Natural gas processing: Forecasted sales of NGLs [Member]
Derivative [Line Items]
Current Volume	6.5	[1],[2],[3]
Forecasted NGL sales designated as normal sales agreements	0.3
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Octane enhancement: Forecasted sales of octane enhancement products [Member]
Derivative [Line Items]
Current Volume	1.0	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Natural gas marketing: Forecasted purchases of natural gas for fuel [Member]
Derivative [Line Items]
Current Volume | ft³	7.2	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | NGL marketing: Forecasted purchases of NGLs and related hydrocarbon products [Member]
Derivative [Line Items]
Current Volume	58.3	[1],[2]
Long Term Volume	0.5	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | NGL marketing: Forecasted sales of NGLs and related hydrocarbon products [Member]
Derivative [Line Items]
Current Volume	66.3	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Refined products marketing: Forecasted purchases of refined products [Member]
Derivative [Line Items]
Current Volume	1.8	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Refined products marketing: Forecasted sales of refined products [Member]
Derivative [Line Items]
Current Volume	1.5	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Crude oil marketing: Forecasted purchases of crude oil [Member]
Derivative [Line Items]
Current Volume	13.1	[1],[2]
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Crude oil marketing: Forecasted sales of crude oil [Member]
Derivative [Line Items]
Current Volume	20.3	[1],[2]
Commodity derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Natural gas marketing: Natural gas storage inventory management activities [Member]
Derivative [Line Items]
Current Volume | ft³	8.9	[1],[2]
Commodity derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Refined products marketing: Refined products inventory management activities [Member]
Derivative [Line Items]
Current Volume	5.1	[1],[2]
Commodity derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Crude oil marketing: Crude oil inventory management activities [Member]
Derivative [Line Items]
Current Volume	0.2	[1],[2]
Commodity derivatives [Member] | Derivatives in mark-to-market relationships [Member] | Natural gas risk management activities [Member]
Derivative [Line Items]
Current Volume | ft³	80.9	[1],[2],[4],[5]
Long Term Volume | ft³	7.4	[1],[2],[4],[5]
Current natural gas hedging volumes designated as an index plus or minus a discount | ft³	51.0
Long-term natural gas hedging volumes designated as an index plus or minus a discount | ft³	2.1
Commodity derivatives [Member] | Derivatives in mark-to-market relationships [Member] | NGL risk management activities [Member]
Derivative [Line Items]
Current Volume	4.0	[1],[2],[5]
Commodity derivatives [Member] | Derivatives in mark-to-market relationships [Member] | Crude oil risk management activities [Member]
Derivative [Line Items]
Current Volume	28.5	[1],[2],[5]
Long Term Volume	2.3	[1],[2],[5]

[1] 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 2017, December 2016 and March 2019, respectively.

[2] 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.

[3] Forecasted sales of NGL volumes under natural gas processing exclude 0.3 MMBbls of additional hedges executed under contracts that have been designated as normal sales agreements.

[4] Current and long-term volumes include 51.0 Bcf and 2.1 Bcf, respectively, of physical derivative instruments that are predominantly priced at a marked-based index plus a premium or minus a discount related to location differences.

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