Quarterly report pursuant to Section 13 or 15(d)

Medical Claims Liability - Schedule of Change in Medical Claims Liability (Details)

v3.10.0.1
Medical Claims Liability - Schedule of Change in Medical Claims Liability (Details) - USD ($)
$ in Millions
9 Months Ended
Sep. 30, 2018
Sep. 30, 2017
Liability for Unpaid Claims and Claims Adjustment Expense [Roll Forward]    
Balance, January 1 $ 4,286 $ 3,929
Less: Reinsurance recoverable 18 5
Balance, January 1, net 4,268 3,924
Acquisitions 1,319 0
Incurred related to:    
Current year 33,465 28,666
Prior years (420) (388)
Total incurred 33,045 28,278
Paid related to:    
Current year 28,194 24,787
Prior years 3,485 3,099
Total paid 31,679 27,886
Balance at September 30, net 6,953 4,316
Plus: Reinsurance recoverable 30 17
Balance, September 30 $ 6,983 $ 4,333