XML 132 R117.htm IDEA: XBRL DOCUMENT v3.20.4
Commitments And Contingencies (Narrative) (Details)
 12 Months Ended
Dec. 31, 2020
USD ($)
Item
$ / Item
Dec. 31, 2005
Item
Derivative [Line Items]    
Number of equity index put option contracts | Item   7
Equity Index Put Option [Member] | Standard & Poor's 500 [Member]    
Derivative [Line Items]    
Number of equity index put option contracts | Item 1  
Probability of falling below strike price, percentage 0.20%  
Index | $ / Item 3,756.07  
Equity Index Put Option [Member] | Standard & Poor's 500 [Member] | Theoretical [Member]    
Derivative [Line Items]    
Maximum discount factor 3.00%  
Maximum payout occurs based on index value | $ $ 147,894,000  
Equity Index Put Option [Member] | Standard & Poor's 500 [Member] | If Contracts Expire [Member]    
Derivative [Line Items]    
Settlement amount | $ $ 0