Consolidated Statement of Income - USD ($) shares in Millions, $ 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										$ 23,874	$ 23,713	$ 22,637
Net investment income										2,379	2,787	2,716
Fee income										445	438	395
Net realized investment gains	[1]									3	79	166
Other revenues										99	145	277
Total revenues		$ 6,674	$ 6,794	$ 6,706	$ 6,626	$ 6,783	$ 6,886	$ 6,785	$ 6,708	26,800	27,162	26,191
Claims and expenses
Claims and claim adjustment expenses										13,723	13,870	13,307
Amortization of deferred acquisition costs										3,885	3,882	3,821
General and administrative expenses										4,079	3,952	3,757
Interest expense										373	369	361
Total claims and expenses		5,465	5,487	5,630	5,478	5,323	5,628	5,884	5,238	22,060	22,073	21,246
Income before income taxes		1,209	1,307	1,076	1,148	1,460	1,258	901	1,470	4,740	5,089	4,945
Income tax expense		343	379	264	315	422	339	218	418	1,301	1,397	1,272
Net income		$ 866	$ 928	$ 812	$ 833	$ 1,038	$ 919	$ 683	$ 1,052	$ 3,439	$ 3,692	$ 3,673
Net income per share
Basic		$ 2.87	$ 3.00	$ 2.56	$ 2.58	$ 3.15	$ 2.72	$ 1.98	$ 2.98	$ 10.99	$ 10.82	$ 9.84
Diluted		$ 2.83	$ 2.97	$ 2.53	$ 2.55	$ 3.11	$ 2.69	$ 1.95	$ 2.95	$ 10.88	$ 10.70	$ 9.74
Weighted average number of common shares outstanding
Basic										310.6	338.8	370.3
Diluted										313.9	342.5	374.3
Cash dividends declared per common share										$ 2.38	$ 2.15	$ 1.96

[1] Total other-than-temporary impairment (OTTI) losses were $(54) million, $(22) million and $(10) million for the years ended December 31, 2015, 2014 and 2013, respectively. Of total OTTI, credit losses of $(52) million, $(26) million and $(15) million for the years ended December 31, 2015, 2014 and 2013, respectively, were recognized in net realized investment gains. In addition, unrealized gains (losses) from other changes in total OTTI of $(2) million, $4 million and $5 million for the years ended December 31, 2015, 2014 and 2013, respectively, were recognized in other comprehensive income (loss) as part of changes in net unrealized gains on investment securities having credit losses recognized in the consolidated statement of income.