Derivative Instruments, Hedging Activities and Fair Value Measurements (Details) bbl in Millions, $ in Millions, ft³ in Billions		12 Months Ended
		Dec. 31, 2015 USD ($) Contract bbl ft³	Dec. 31, 2013 USD ($) Contract	Oct. 14, 2014 USD ($)
Interest rate derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Forward Starting Swaps [Member]
Derivative [Line Items]
Number of derivative instruments settled | Contract			16
Notional amount of settled derivative instruments | $			$ 1,000.0
Accumulated other comprehensive income (loss) related to interest rate derivative instruments | $			$ (168.8)
Date through which gain or loss is amortized		March-23
Interest rate derivatives [Member] | Derivatives in fair value hedging relationships [Member]
Derivative [Line Items]
Loss (gain) recognized due to settlement of derivative instruments | $				$ (27.6)
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)		0.82%
Interest rate derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Senior Notes AA [Member]
Derivative [Line Items]
Loss (gain) recognized due to settlement of derivative instruments | $				(17.6)
Date through which gain or loss is amortized		Jan-16
Interest rate derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Senior Notes LL [Member]
Derivative [Line Items]
Loss (gain) recognized due to settlement of derivative instruments | $				$ (10.0)
Date through which gain or loss is amortized		Oct-19
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	[1],[2]	9.1
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Natural gas processing: Forecasted sales of NGLs [Member]
Derivative [Line Items]
Current Volume	[1],[2]	2.1
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	[1],[2]	2.4
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	[1],[2]	28.7
Long Term Volume	[1],[2]	0.4
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	[1],[2]	42.2
Long Term Volume	[1],[2]	0.1
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],[2]	2.7
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],[2]	0.8
Long Term Volume	[1],[2]	0.1
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Crude oil marketing: Forecasted purchases of crude oil [Member]
Derivative [Line Items]
Current Volume	[1],[2]	15.0
Commodity derivatives [Member] | Derivatives in cash flow hedging relationships [Member] | Crude oil marketing: Forecasted sales of crude oil [Member]
Derivative [Line Items]
Current Volume	[1],[2]	17.6
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	[1],[2]	10.7
Commodity derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Refined products marketing: Refined products inventory management activities [Member]
Derivative [Line Items]
Current Volume	[1],[2]	1.3
Commodity derivatives [Member] | Derivatives in fair value hedging relationships [Member] | Crude oil marketing: Crude oil inventory management activities [Member]
Derivative [Line Items]
Current Volume	[1],[2]	0.7
Commodity derivatives [Member] | Derivatives in mark-to-market relationships [Member] | Natural gas risk management activities [Member]
Derivative [Line Items]
Current Volume | ft³	[1],[2],[3],[4]	48.2
Long Term Volume | ft³	[1],[2],[3],[4]	8.2
Current natural gas hedging volumes designated as an index plus or minus a discount | ft³		24.3
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	[1],[2],[4]	1.8
Commodity derivatives [Member] | Derivatives in mark-to-market relationships [Member] | Crude oil risk management activities [Member]
Derivative [Line Items]
Current Volume	[1],[2],[4]	11.8

[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, January 2017 and March 2018, 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] Current and long-term volumes include 24.3 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.

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