Consolidated Statements Of Income - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Revenues:
Premiums									$ 52,409	$ 45,959	$ 38,829
Services									1,406	2,164	2,109
Investment income									474	377	375
Total revenues	$ 13,361	$ 13,363	$ 13,732	$ 13,833	$ 12,328	$ 12,238	$ 12,222	$ 11,712	54,289	48,500	41,313
Operating expenses:
Benefits									44,269	38,166	32,564
Operating costs									7,318	7,639	6,355
Depreciation and amortization									355	333	333
Total operating expenses									51,942	46,138	39,252
Income from operations									2,347	2,362	2,061
Gain on sale of business									270	0	0
Interest expense									186	192	140
Income before income taxes	246	648	793	744	287	551	646	686	2,431	2,170	1,921
Provision for income taxes									1,155	1,023	690
Net income	$ 101	$ 314	$ 431	$ 430	$ 145	$ 290	$ 344	$ 368	$ 1,276	$ 1,147	$ 1,231
Basic earnings per common share (in dollars per share)	$ 0.68	$ 2.11	$ 2.88	$ 2.86	$ 0.96	$ 1.87	$ 2.22	$ 2.37	$ 8.54	$ 7.44	$ 7.81
Diluted earnings per common share (in dollars per share)	$ 0.67	$ 2.09	$ 2.85	$ 2.82	$ 0.94	$ 1.85	$ 2.19	$ 2.35	8.44	7.36	7.73
Dividends declared per common share (in dollars per share)									$ 1.15	$ 1.11	$ 1.07