Asset Retirement Obligations (Tables)

9 Months Ended

Sep. 30, 2020

Asset Retirement Obligation Disclosure [Abstract]

Schedule of Reconciliation of the Carrying Amount of AROs

A reconciliation of the beginning and ending aggregate carrying amount of AROs is as follows:

(millions)	Amount
AROs at December 31, 2019	$	489
Liabilities settled		(4	)
Accretion expense		17
Revisions in estimated cash flows (1)		89
AROs at September 30, 2020	$	591

(1) The increase in 2020 reflects revisions from the nuclear decommissioning cost study.