XML 124 R101.htm IDEA: XBRL DOCUMENT v3.20.4
Note 12 - Commitments and Contingencies (Details) - Asset Retirement Obligation Activity - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Asset Retirement Obligation Activity [Abstract]    
Asset Retirement Obligations at start of period $ 48 $ 48
Liabilities incurred in the current period 1 3
Liabilities settled in the current period (9) (6)
Accretion expense 1 2
Revision in estimated cash flows   1
Asset Retirement Obligations at end of period $ 41 $ 48