Derivatives and Risk Management Activities (Details) - Jun. 30, 2015 bbl in Millions, Mcf in Millions, MWh in Millions	bbl / d MWh Mcf bbl
Net long position associated with crude oil purchases
Commodity Price Risk Hedging:
Average derivative positions notional amount per day (in barrels) | bbl / d	151,600
Derivative position notional amount (in barrels or Mcf)	4.7
Net short time spread position hedging anticipated crude oil lease gathering purchases
Commodity Price Risk Hedging:
Average derivative positions notional amount per day (in barrels) | bbl / d	17,800
Derivative position notional amount (in barrels or Mcf)	7.6
Crude oil grade spread positions
Commodity Price Risk Hedging:
Average derivative positions notional amount per day (in barrels) | bbl / d	35,800
Derivative position notional amount (in barrels or Mcf)	5.5
Net short position related to anticipated sales of natural gas inventory and base gas requirements
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf) | Mcf	13.9
Net short position related to anticipated purchases and sales of crude oil, NGL and refined products inventory
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	15.3
Positions hedging risk of not utilizing storage capacity
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	0.8
Long natural gas position for natural gas purchases
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf) | Mcf	15.2
Short propane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	2.9
Short butane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	0.9
Short WTI position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	0.3
Long power position for power supply requirements
Commodity Price Risk Hedging:
Derivative position notional amount (in megawatt hours) | MWh	0.5