Consolidated Statements Of Shareholders' Equity (USD $) In Millions, unless otherwise specified	Total	Common Shares	Common Shares in Treasury	Additional Paid-in Capital	Retained Earnings	Deferred Compensation Obligation	Accumulated Other Comprehensive Income	Net unrealized appreciation on investments	Cumulative Translation Adjustment	Accumulated Defined Benefit Plans Adjustment [Member]	Common Shares Issued To Employee Trust
Balance - beginning of year at Dec. 31, 2009 (Scenario, Previously Reported)					$ 2,818
Cumulative effect of adjustment resulting from adoption of new accounting guidance (Restatement Adjustment)					(116)
Balance - beginning of year at Dec. 31, 2009		10,503	(3)	5,526	2,702	2		657	240	(74)	(2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares redeemed under employee share-based compensation plans		71		(64)
Exercise of stock options		30		23
Dividends declared on Common Shares-par value reduction		(443)
Common shares repurchased			(303)
Common Shares issued in treasury, net of net shares redeemed under employee share-based compensation plans			(24)
Share-based compensation expense and other				139
Tax (expense) benefit on share-based compensation expense				(1)
Net income	3,085				3,085
Funding of dividends declared from Additional paid-in capital
Dividends declared on Common Shares
Decrease to obligation
Change in year, net of income tax expense of $(198), $(157) and $(152)								742
Change in year, net of income tax benefit (expense) of $(35), $1, and $29									22
Change in year, net of income tax benefit of $12, $(3) and $(4)										7
Movement In Common Shares Issued To Employee Trust
Balance - end of year at Dec. 31, 2010 (Scenario, Previously Reported)
Balance - end of year at Dec. 31, 2010	22,835	10,161	(330)	5,623	5,787	2	1,594	1,399	262	(67)	(2)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares redeemed under employee share-based compensation plans				(104)
Exercise of stock options		47		16
Dividends declared on Common Shares-par value reduction		(113)
Common shares repurchased			(132)
Common Shares issued in treasury, net of net shares redeemed under employee share-based compensation plans			135
Share-based compensation expense and other				139
Tax (expense) benefit on share-based compensation expense				6
Net income	1,540				1,540
Funding of dividends declared from Additional paid-in capital				(354)	354
Dividends declared on Common Shares					(354)
Decrease to obligation						(2)
Change in year, net of income tax expense of $(198), $(157) and $(152)								316
Change in year, net of income tax benefit (expense) of $(35), $1, and $29									(4)
Change in year, net of income tax benefit of $12, $(3) and $(4)										5
Movement In Common Shares Issued To Employee Trust	2
Balance - end of year at Dec. 31, 2011 (Scenario, Previously Reported)
Balance - end of year at Dec. 31, 2011	24,332	10,095	(327)	5,326	7,327		1,911	1,715	258	(62)
Cumulative effect of adjustment resulting from adoption of new accounting guidance (Restatement Adjustment)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net shares redeemed under employee share-based compensation plans				(93)
Exercise of stock options				(7)
Dividends declared on Common Shares-par value reduction		(504)
Common shares repurchased			(7)
Common Shares issued in treasury, net of net shares redeemed under employee share-based compensation plans			175
Share-based compensation expense and other				135
Tax (expense) benefit on share-based compensation expense				18
Net income	2,706				2,706
Funding of dividends declared from Additional paid-in capital				(200)	200
Dividends declared on Common Shares					(200)
Decrease to obligation
Change in year, net of income tax expense of $(198), $(157) and $(152)								918
Change in year, net of income tax benefit (expense) of $(35), $1, and $29									81
Change in year, net of income tax benefit of $12, $(3) and $(4)										(23)
Movement In Common Shares Issued To Employee Trust
Balance - end of year at Dec. 31, 2012	$ 27,531	$ 9,591	$ (159)	$ 5,179	$ 10,033		$ 2,887	$ 2,633	$ 339	$ (85)