Unaudited Consolidated Quarterly Financial Data (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Condensed Consolidating Statement of Operations [Line Items]
Net premium income	$ 4,489	$ 4,841	$ 4,888	$ 4,854	$ 4,910	$ 5,028	$ 5,013	$ 5,184	$ 19,072	$ 20,135	$ 22,148
Net investment income	808	841	843	827	826	821	813	833	3,319	3,293	3,473
Realized investment gains (losses)	143	16	102	(46)	20	22	201	156
Other income	74	38	5	5	45	15	17	35	122	112	92
Total revenues	5,514	5,736	5,838	5,640	5,801	5,886	6,044	6,208	22,728	23,939	25,364
Total benefits and expenses	4,439	4,662	4,600	4,536	4,773	4,817	4,686	4,847	18,237	19,123	21,062
Earnings before income taxes	1,075	1,074	1,238	1,104	1,028	1,069	1,358	1,361	4,491	4,816	4,302
Total income tax expense	372	368	428	372	353	367	469	469	1,540	1,658	1,436
Net earnings	$ 703	$ 706	$ 810	$ 732	$ 675	$ 702	$ 889	$ 892
Net earnings per basic share	$ 1.57	$ 1.56	$ 1.79	$ 1.61	$ 1.46	$ 1.51	$ 1.91	$ 1.91	$ 6.54	$ 6.80	$ 6.14
Net earnings per diluted share	$ 1.57	$ 1.56	$ 1.78	$ 1.60	$ 1.45	$ 1.50	$ 1.90	$ 1.90	$ 6.50	$ 6.76	$ 6.11