Annual report pursuant to Section 13 and 15(d)

Capital (Details)

v3.20.4
Capital (Details)
 1 Months Ended 12 Months Ended
Dec. 31, 2020
$ / shares
Mar. 31, 2020
$ / shares
Mar. 31, 2019
$ / shares
Dec. 31, 2020
$ / shares
shares
Dec. 31, 2019
$ / shares
shares
Dec. 31, 2018
$ / shares
shares
Jan. 11, 2021
Class of Stock [Line Items]              
Special dividends paid per sub-share certificate (in dollars per share)   $ 16.00   $ 16.00 $ 4.25 $ 3.00  
Sub shares              
Class of Stock [Line Items]              
Ratio of certificates to sub-shares       0.0003      
Number of shares repurchased and retired (in shares) | shares       0 6,258 59,185  
Sub shares | Subsequent event              
Class of Stock [Line Items]              
Ratio of sub-shares to common stock             1
Cash dividend | Sub shares              
Class of Stock [Line Items]              
Dividend paid per sub-share (in USD per share)   10.00 $ 1.75        
Special dividend | Sub shares              
Class of Stock [Line Items]              
Dividend paid per sub-share (in USD per share) $ 10.00 $ 6.00 $ 4.25