Risk Management (Notional Amounts and Terms of Company's Derivative Financial Instruments) (Details) bcf in Millions, MMBbls in Millions	Mar. 31, 2020 MMBbls bcf	Dec. 31, 2019 MMBbls bcf
Propane Crude And Heating Oil | Fixed Price Payor
Derivative [Line Items]
Derivative, notional amount | MMBbls	43.1	33.5
Propane Crude And Heating Oil | Fixed Price Receiver
Derivative [Line Items]
Derivative, notional amount | MMBbls	45.4	36.6
Natural Gas [Member] | Fixed Price Payor
Derivative [Line Items]
Derivative, notional amount | bcf	6.5	3.7
Natural Gas [Member] | Fixed Price Receiver
Derivative [Line Items]
Derivative, notional amount | bcf	10.7	8.7