XML 63 R53.htm IDEA: XBRL DOCUMENT v3.20.2
Asset Retirement Obligations (Schedule of Reconciliation of the Carrying Amount of AROs) (Detail)
$ in Millions
6 Months Ended
Jun. 30, 2020
USD ($)
Asset Retirement Obligation Disclosure [Abstract]  
Beginning balance $ 489
Liabilities settled (2)
Accretion expense 11
Revisions in estimated cash flows 89 [1]
Ending balance $ 587
[1] The increase in 2020 reflects revisions from the nuclear decommissioning cost study.