Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Common shares in treasury [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] The Chubb Corporation [Member]	Retained Earnings [Member]	Accumulated Net Unrealized Investment Gain (Loss) [Member]	Cumulative Translation Adjustment [Member]	Pension Liability Adjustment [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance - beginning of period at Dec. 31, 2014		$ 8,055	$ (1,448)	$ 5,145		$ 16,644	$ 1,851	$ (581)	$ (79)
Dividends declared on Common Shares – par value reduction		(222)
Net shares redeemed under employee share-based compensation plans			183	(163)	$ 0
Shares Issued for Chubb Corp Acquisition		0			0
Common Shares repurchased			(734)
Exercise of stock options				(29)
Share-based compensation expense and other				111
Funding of dividends declared to Retained earnings				(217)
Net income	$ 1,623					1,623
Funding of dividends declared from Additional paid-in capital						217
Dividends declared on Common Shares						(217)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $(477) and $81							(294)
Amounts reclassified from AOCI, net of income tax benefit of $5 and $14							(17)
Change in period, net of income tax benefit (expense) of $(472) and $95							(311)
Change in period, net of income tax benefit (expense) of $(11) and $7								(278)
Change in period, net of income tax benefit (expense) of $1 and $(2)									5
Balance - end of period at Jun. 30, 2015	29,555	7,833	(1,999)	4,847		18,267	1,540	(859)	(74)	$ 607
Balance - beginning of period at Dec. 31, 2015	29,135	7,833	(1,922)	4,481		19,478	874	(1,539)	(70)
Dividends declared on Common Shares – par value reduction		0
Net shares redeemed under employee share-based compensation plans			345	(358)	323
Shares Issued for Chubb Corp Acquisition		3,288			$ 11,916
Common Shares repurchased			0
Exercise of stock options				(37)
Share-based compensation expense and other				170
Funding of dividends declared to Retained earnings				(637)
Net income	1,165					1,165
Funding of dividends declared from Additional paid-in capital						637
Dividends declared on Common Shares						(637)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $(477) and $81							1,375
Amounts reclassified from AOCI, net of income tax benefit of $5 and $14							155
Change in period, net of income tax benefit (expense) of $(472) and $95							1,530
Change in period, net of income tax benefit (expense) of $(11) and $7								382
Change in period, net of income tax benefit (expense) of $1 and $(2)									4
Balance - end of period at Jun. 30, 2016	$ 47,226	$ 11,121	$ (1,577)	$ 15,858		$ 20,643	$ 2,404	$ (1,157)	$ (66)	$ 1,181