Commitments and Contingencies Environmental Requirements - Water and Waste (Details) - Federal Coal Ash Regulation [Domain]	Mar. 31, 2020
Site Contingency [Line Items]
Number of sites where regulated ash units will still be in operation at a specified date	6
Number of sites where statistically significant increases over established groundwater standards exist	4
Number of sites where corrective action options are being evaluated for locations with statistically significant increases above background concentrations	2
Number of impoundments where closure plans will be expedited	1