XML 80 R69.htm IDEA: XBRL DOCUMENT v3.20.2
Equity - Additional Information (Detail) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Oct. 31, 2020
May 31, 2018
Sep. 30, 2020
Sep. 30, 2019
Sep. 30, 2020
Sep. 30, 2019
Dec. 31, 2019
Class of Stock [Line Items]              
Treasury stock, shares (in shares)     485,597   485,597   485,810
Convertible preferred stock, shares outstanding (in shares)     0   0   0
Release of common stock held in trust (in shares)     0 0 213 0  
Number of shares authorized to be repurchased (in shares)   42,777          
Treasury shares of common stock (in shares)     303,835   303,835    
Repurchases of common stock     $ 14   $ 14   $ 12
Subsequent Event              
Class of Stock [Line Items]              
Release of common stock held in trust (in shares) 4,332            
Iberdrola Renewables Holding, Inc              
Class of Stock [Line Items]              
Percentage of equity owned by parent     81.50%   81.50%