Annual report pursuant to Section 13 and 15(d)

Subsequent Events (Details)

v3.20.4
Subsequent Events (Details) - $ / shares
Feb. 17, 2021
Jan. 11, 2021
Dec. 31, 2020
Dec. 31, 2019
Subsequent Event [Line Items]        
Sub-share certificates of proprietary interest, par value (in dollars per share)     $ 0.0333 $ 0.0333
Certificates of proprietary interest, par value (in dollars per share)     $ 100 $ 100
Certificates of proprietary interest, outstanding (in shares)     0 0
Sub-share certificates of proprietary interest, outstanding (in shares)     7,756,156 7,756,156
Subsequent event        
Subsequent Event [Line Items]        
Sub-share certificates of proprietary interest, par value (in dollars per share)   $ 0.01    
Sub-share certificates of proprietary interest, outstanding (in shares)   7,756,156    
Subsequent event | Dividend declared        
Subsequent Event [Line Items]        
Annual cash dividend $ 2.75