Consolidated Statements of Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues
Premiums									$ 36,113	$ 32,491	$ 30,824
Net investment income									1,480	1,226	1,147
Total revenues	$ 14,300	$ 11,457	$ 11,480	$ 11,413	$ 10,632	$ 10,372	$ 10,374	$ 10,428	48,650	41,806	39,838
Benefits and Expenses
Medical costs and other benefit expenses									27,528	25,263	24,341
Pharmacy and other service costs									4,793	2,456	2,468
Selling, general and administrative expenses									11,934	10,030	9,790
Amortization of other acquired intangible assets									235	115	151
Total operating expenses									44,490	37,864	36,750
Income from operations									4,160	3,942	3,088
Interest expense and other									(498)	(252)	(278)
Debt extinguishment costs						(321)			0	(321)	0
Net realized investment gains (losses)									(81)	237	169
Income (loss) before income taxes	228	1,033	1,102	1,218	758	824	1,134	890	3,581	3,606	2,979
Total income taxes									935	1,374	1,136
Net Income									2,646	2,232	1,843
Less: net income (loss) attributable to noncontrolling interests									9	(5)	(24)
Shareholders' net income	$ 144	$ 772	$ 806	$ 915	$ 266	$ 560	$ 813	$ 598	$ 2,637	$ 2,237	$ 1,867
Shareholders' net income per share:
Basic	$ 0.56	$ 3.18	$ 3.32	$ 3.78	$ 1.09	$ 2.25	$ 3.2	$ 2.34	$ 10.69	$ 8.92	$ 7.31
Diluted	0.55	3.14	3.29	3.72	1.07	2.21	3.15	2.3	$ 10.54	$ 8.77	$ 7.19
Dividends declared per share	$ 0	$ 0	$ 0	$ 0.04	$ 0	$ 0	$ 0	$ 0.04
Fees and other revenues [Member]
Revenues
Pharmacy revenues, fees and other revenues									$ 5,578	$ 5,110	$ 4,901
Pharmacy revenues [Member]
Revenues
Pharmacy revenues, fees and other revenues									$ 5,479	$ 2,979	$ 2,966