Annual report pursuant to Section 13 and 15(d)

Medical Claims Liability - Incurred Claims and Allocated Claims Adjustment Expenses (Details)

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Medical Claims Liability - Incurred Claims and Allocated Claims Adjustment Expenses (Details) - Health insurance product line
claim in Millions, $ in Millions
Dec. 31, 2019
USD ($)
claim
Dec. 31, 2018
USD ($)
Dec. 31, 2017
USD ($)
Claims Development [Line Items]      
Short-duration insurance contracts, incurred claims and allocated claim adjustment expense, net $ 157,521    
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, expected development on reported claims $ 0    
Short-duration Insurance contracts, number of reported claims | claim 260.2    
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, expected development on reported claims $ 88    
Short-duration Insurance contracts, number of reported claims | claim 281.7    
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, expected development on reported claims $ 5,347    
Short-duration Insurance contracts, number of reported claims | claim 290.2