Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions		Total	Common stock:	Additional paid-in capital:	Retained earnings:	Accumulated other comprehensive income (loss):	Treasury stock:
Balance, beginning of period at Dec. 31, 2016			$ 135	$ 1,908	$ 25,981	$ 2,630	$ (10,172)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options				10
Share-based compensation				12
Treasury stock reissued				10			15
Net earnings		$ 592			592
Dividends to shareholders					(173)
Unrealized foreign currency translation gains (losses) during period, net of income taxes						333
Unrealized gains (losses) on fixed maturity securities during period, net of income taxes and reclassification adjustments	[1]					(331)
Unrealized gains (losses) on derivatives during period, net of income taxes						2
Pension liability adjustment during period, net of income taxes						(2)
Purchases of treasury stock							(610)
Balance, end of period at Mar. 31, 2017		20,340	135	1,940	26,400	2,632	(10,767)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2016-01	[1]				0	0
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2018-02	[1]				0	0
Balance, beginning of period at Dec. 31, 2017		24,598	135	2,052	29,895	4,028	(11,512)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of stock options				14
Share-based compensation				10
Treasury stock reissued				13			16
Net earnings		717			717
Dividends to shareholders					(203)
Unrealized foreign currency translation gains (losses) during period, net of income taxes						447
Unrealized gains (losses) on fixed maturity securities during period, net of income taxes and reclassification adjustments	[1]					(984)
Unrealized gains (losses) on derivatives during period, net of income taxes						2
Pension liability adjustment during period, net of income taxes						(34)
Purchases of treasury stock							(309)
Balance, end of period at Mar. 31, 2018		$ 24,287	$ 135	$ 2,089	30,183	3,685	$ (11,805)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2016-01	[1]				148	(148)
Cumulative effect of change in accounting principle, net of income taxes | Accounting Standards Update 2018-02	[1]				$ (374)	$ 374

[1] See Note 1 of the Notes to the Consolidated Financial Statements for the adoption of accounting guidance on January 1, 2018.