Annual report pursuant to Section 13 and 15(d)

Medical Claims Liability - Cumulative incurred and Paid Claims (Details)

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Medical Claims Liability - Cumulative incurred and Paid Claims (Details) - Health insurance product line - USD ($)
$ in Millions
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Claims Development [Line Items]      
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net $ 157,521    
Short-duration insurance contracts, cumulative paid claims and allocated claim adjustment expense, net 150,068    
Short-duration insurance contracts, liability for unpaid claims and allocated claim adjustment expense, net, not separately presented 7,453    
Short-duration insurance contracts, accident year 2017      
Claims Development [Line Items]      
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net 46,950 $ 46,994 $ 47,574
Short-duration insurance contracts, cumulative paid claims and allocated claim adjustment expense, net 46,904 46,767 $ 42,205
Short-duration insurance contracts, accident year 2018      
Claims Development [Line Items]      
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net 50,944 51,572  
Short-duration insurance contracts, cumulative paid claims and allocated claim adjustment expense, net 50,682 $ 45,039  
Short-duration insurance contracts, accident year 2019      
Claims Development [Line Items]      
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net 59,627    
Short-duration insurance contracts, cumulative paid claims and allocated claim adjustment expense, net $ 52,482