Risk Management (Notional Amounts and Terms of Company's Derivative Financial Instruments) (Details) bcf in Millions, MMBbls in Millions	Jun. 30, 2020 MMBbls bcf	Dec. 31, 2019 MMBbls bcf
Propane Crude And Heating Oil | Fixed Price Payor
Derivative [Line Items]
Derivative, notional amount | MMBbls	64.4	33.5
Propane Crude And Heating Oil | Fixed Price Receiver
Derivative [Line Items]
Derivative, notional amount | MMBbls	69.8	36.6
Natural Gas [Member] | Fixed Price Payor
Derivative [Line Items]
Derivative, notional amount | bcf	10.2	3.7
Natural Gas [Member] | Fixed Price Receiver
Derivative [Line Items]
Derivative, notional amount | bcf	17.5	8.7