Derivatives and Risk Management Activities (Details) bbl in Millions, Mcf in Millions, MWh in Millions	9 Months Ended
	Sep. 30, 2015 MMBbls / mo 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	159,000
Derivative position notional amount (in barrels or Mcf)	4.9
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	12,900
Derivative position notional amount (in barrels or Mcf)	5.9
Crude oil grade spread positions
Commodity Price Risk Hedging:
Average derivative positions notional amount per day (in barrels) | bbl / d	8,200
Derivative position notional amount (in barrels or Mcf)	2.2
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	15.8
Net short position related to anticipated net sales of crude oil and NGL inventory
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	22.7
Positions hedging risk of not utilizing storage capacity
Commodity Price Risk Hedging:
Average derivative positions notional amount per month (in millions of barrels) | MMBbls / mo	2.0
PLA crude oil net short position
Commodity Price Risk Hedging:
Average derivative positions notional amount per day (in barrels) | bbl / d	400
Derivative position notional amount (in barrels or Mcf)	0.2
PLA crude oil long call option position
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	1.7
Long natural gas position for natural gas purchases
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf) | Mcf	9.7
Short propane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	2.2
Short butane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	0.6
Short WTI position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels or Mcf)	0.2
Long power position for power supply requirements
Commodity Price Risk Hedging:
Derivative position notional amount (in megawatt hours) | MWh	0.5