Derivative Instruments, Hedging Activities and Fair Value Measurements (Details) bbl in Millions, $ in Millions, ft³ in Billions		12 Months Ended
		Dec. 31, 2016 USD ($) Contract bbl ft³	Dec. 31, 2014 USD ($)
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 Swaps Hedging Senior Notes OO [Member] | Derivatives in fair value hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract		10
Type of Derivatives Outstanding		fixed-to-floating swaps
Notional Amount | $		$ 750.0
Derivative, Inception Date		May 01, 2015
Expected Termination Date		May 01, 2018
Rate Swap, fixed rate		1.65%
Rate Swap, floating rate		1.36%
Interest Rate Swaps Hedging Senior Notes AA [Member] | Derivatives in fair value hedging relationships [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 Swaps Hedging Senior Notes LL [Member] | Derivatives in fair value hedging relationships [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
Forward Starting Swaps [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of interest rate derivatives entered into during the year | Contract		8
Life of associated future debt		30 years
Accumulated other comprehensive income (loss) related to interest rate derivative instruments | $		$ 6.1
Forward Starting Swaps B [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Number of Derivatives Outstanding | Contract		4
Type of Derivatives Outstanding		forward starting swaps
Notional Amount | $		$ 275.0
Expected Termination Date		May 01, 2018
Average Rate Locked		2.02%
Octane enhancement: Forecasted purchases of NGLs [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	1.4
Octane enhancement: Forecasted sales of octane enhancement products [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	1.3
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]
Derivative [Line Items]
Derivative instruments, current volume | ft³	[1],[2]	21.6
Designated as Hedging Instrument [Member] | Natural gas processing: Forecasted sales of NGLs [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2],[3]	4.3
Forecasted NGL sales designated as normal sales agreements		1.2
Designated as Hedging Instrument [Member] | Natural gas marketing: Forecasted purchases of natural gas for fuel [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume | ft³	[1],[2]	1.8
Designated as Hedging Instrument [Member] | Natural gas marketing: Natural gas storage inventory management activities [Member] | Derivatives in fair value hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume | ft³	[1],[2]	8.0
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted purchases of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	101.9
Designated as Hedging Instrument [Member] | NGL marketing: Forecasted sales of NGLs and related hydrocarbon products [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	124.1
Designated as Hedging Instrument [Member] | Refined products marketing: Forecasted purchases of refined products [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	0.5
Designated as Hedging Instrument [Member] | Refined products marketing: Forecasted sales of refined products [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	0.5
Designated as Hedging Instrument [Member] | Refined products marketing: Refined products inventory management activities [Member] | Derivatives in fair value hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	1.2
Designated as Hedging Instrument [Member] | Crude oil marketing: Forecasted purchases of crude oil [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	11.5
Designated as Hedging Instrument [Member] | Crude oil marketing: Forecasted sales of crude oil [Member] | Derivatives in cash flow hedging relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2]	17.1
Not Designated as Hedging Instrument [Member] | Natural gas risk management activities [Member] | Derivatives in mark-to-market relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume | ft³	[1],[2],[4],[5]	156.6
Derivative instruments, long-term volume | ft³	[1],[2],[4],[5]	8.3
Current natural gas hedging volumes designated as an index plus or minus a discount | ft³		35.3
Long-term natural gas hedging volumes designated as an index plus or minus a discount | ft³		0.9
Not Designated as Hedging Instrument [Member] | Refined products risk management activities [Member] | Derivatives in mark-to-market relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2],[5]	0.1
Not Designated as Hedging Instrument [Member] | NGL risk management activities [Member] | Derivatives in mark-to-market relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2],[5]	18.7
Not Designated as Hedging Instrument [Member] | Crude oil risk management activities [Member] | Derivatives in mark-to-market relationships [Member]
Derivative [Line Items]
Derivative instruments, current volume	[1],[2],[5]	27.8

[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, June 2017 and March 2020, 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 NGL sales volumes under Natural gas processing exclude 1.2 MMBbls of additional hedges executed under contracts that have been designated as normal sales agreements.

[4] Current and long-term volumes include 35.3 Bcf and 0.9 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.