Unaudited Consolidated Quarterly Financial Data (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Premium Revenue	$ 4,910	$ 5,028	$ 5,013	$ 5,184	$ 5,643	$ 5,660	$ 5,467	$ 5,378	$ 20,135	$ 22,148	$ 20,362
Net investment income	826	821	813	833	876	869	845	882	3,293	3,473	3,280
Realized investment gains (losses)	20	22	201	156	(171)	286	(418)	(45)
Other income	45	15	17	35	27	32	8	25	112	92	81
Total revenues	5,801	5,886	6,044	6,208	6,375	6,847	5,902	6,240	23,939	25,364	22,171
Total benefits and expenses	4,773	4,817	4,686	4,847	5,495	5,367	5,161	5,038	19,123	21,062	19,221
Earnings before income taxes	1,028	1,069	1,358	1,361	880	1,480	741	1,202	4,816	4,302	2,950
Total income tax expense	353	367	469	469	299	463	258	417	1,658	1,436	1,013
Net earnings	$ 675	$ 702	$ 889	$ 892	$ 581	$ 1,017	$ 483	$ 785
Net earnings per basic share	$ 1.46	$ 1.51	$ 1.91	$ 1.91	$ 1.24	$ 2.17	$ 1.04	$ 1.68	$ 6.80	$ 6.14	$ 4.16
Net earnings per diluted share	$ 1.45	$ 1.50	$ 1.90	$ 1.90	$ 1.24	$ 2.16	$ 1.03	$ 1.68	$ 6.76	$ 6.11	$ 4.12