CONSOLIDATED STATEMENTS OF INCOME - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Revenue:    
Premium revenue $ 4,323 $ 4,648
Service revenue 134 131
Premium tax revenue 104 111
Health insurer fees reimbursed 61 0
Investment income and other revenue 24 14
Total revenue 4,646 4,904
Operating expenses:    
Medical care costs 3,722 4,111
Cost of service revenue 120 122
General and administrative expenses 352 439
Premium tax expenses 104 111
Health insurer fees 75 0
Depreciation and amortization 26 39
Restructuring and separation costs 25 0
Total operating expenses 4,424 4,822
Operating income 222 82
Other expenses (income), net:    
Interest expense 33 26
Other expense (income), net 10 (75)
Total other expenses (income), net 43 (49)
Income before income tax expense 179 131
Income tax expense 72 54
Net income $ 107 $ 77
Net income per share:    
Basic (in dollars per share) $ 1.79 $ 1.38
Diluted (in dollars per share) $ 1.64 $ 1.37