XML 107 R90.htm IDEA: XBRL DOCUMENT v3.19.1
Note 11 - Commitments and Contingencies (Details) - Asset Retirement Obligation Activity - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Asset Retirement Obligation Activity [Abstract]    
Asset Retirement Obligations at start of period $ 43 $ 38
Liabilities incurred in the current period 3 2
Liabilities settled in the current period (3) (1)
Accretion expense 2 1
Revision in estimated cash flows 3 3
Asset Retirement Obligations at end of period $ 48 $ 43