Commitments And Contingencies (Details) - USD ($) $ in Thousands		6 Months Ended
	Aug. 03, 2020	Jun. 30, 2020
Commitments And Contingencies [Line Items]
Aggregate amount accrued for loss contingencies		$ 21,561
Amount probable of recovery through insurance		9,083
Insurance reserve for employee medical benefit program		$ 1,852
Peoples Gas Acquisition [Member]
Commitments And Contingencies [Line Items]
Pipeline term		7 years
Pipeline cost		$ 120,000
Customer rate credits		$ 23,000
Subsequent Event [Member]
Commitments And Contingencies [Line Items]
Insurance proceeds	$ 2,874