Consolidated Statements Of Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues:
Premiums									$ 53,021	$ 52,409	$ 45,959
Services									969	1,406	2,164
Investment income									389	474	377
Total revenues	$ 12,878	$ 13,694	$ 14,007	$ 13,800	$ 13,361	$ 13,363	$ 13,732	$ 13,833	54,379	54,289	48,500
Operating expenses:
Benefits									45,007	44,269	38,166
Operating costs									7,277	7,318	7,639
Depreciation and amortization									354	355	333
Total operating expenses									52,638	51,942	46,138
Income from operations									1,741	2,347	2,362
Gain on sale of business									0	270	0
Interest expense									189	186	192
Income before income taxes	(486)	902	636	500	246	648	793	744	1,552	2,431	2,170
Provision for income taxes									938	1,155	1,023
Net income	$ (401)	$ 450	$ 311	$ 254	$ 101	$ 314	$ 431	$ 430	$ 614	$ 1,276	$ 1,147
Basic earnings per common share (in dollars per share)	$ (2.68)	$ 3.01	$ 2.08	$ 1.70	$ 0.68	$ 2.11	$ 2.88	$ 2.86	$ 4.11	$ 8.54	$ 7.44
Diluted earnings per common share (in dollars per share)	$ (2.68)	$ 2.98	$ 2.06	$ 1.68	$ 0.67	$ 2.09	$ 2.85	$ 2.82	4.07	8.44	7.36
Dividends declared per common share (in dollars per share)									$ 1.16	$ 1.15	$ 1.11