Derivatives and Risk Management Activities - Commodity Price Risk Hedging (Details) bbl in Millions	9 Months Ended
	Sep. 30, 2019 TWh bbl Bcf MMBbls
Net long position associated with crude oil purchases
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf)	3.1
Net short time spread position hedging anticipated crude oil lease gathering purchases
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf)	6.9
Net crude oil basis spread position
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf)	23.1
Net short position related to anticipated net sales of crude oil and NGL inventory
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf)	12.1
Positions hedging risk storage capacity will not be utilized
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf)	0.9
Long natural gas position for natural gas purchases and operational needs
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf) | Bcf	59.5
Short propane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf) | MMBbls	5.7
Short butane position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf) | MMBbls	2.7
Short condensate WTI position related to subsequent sale of products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf) | MMBbls	0.7
Net long position contracts related to anticipated sales of specification products
Commodity Price Risk Hedging:
Derivative position notional amount (in barrels, MMbls or Bcf) | MMBbls	0.1
Long power position for power supply requirements
Commodity Price Risk Hedging:
Derivative position notional amount (in Terawatt hours) | TWh	1.0