Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Common Stock [Member] The Chubb Corporation [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)
Shares Issued for Chubb Corp Acquisition		0				$ 0
Dividends declared on Common Shares – par value reduction		(222)
Common Shares repurchased				(734)
Net shares redeemed under employee share-based compensation plans				208	(157)	0
Exercise of stock options					(43)
Share-based compensation expense and other					155
Funding of dividends declared to Retained earnings					(435)
Net income	$ 2,151						2,151
Funding of dividends declared from Additional paid-in capital							435
Dividends declared on Common Shares							(435)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $(559) and $102								(594)
Amounts reclassified from AOCI, net of income tax benefit of $16 and $10								28
Change in period, net of income tax benefit (expense) of $(543) and $112								(566)
Change in period, net of income tax benefit (expense) of $(18) and $35									(825)
Change in period, net of income tax expense of nil and $(2)										8
Balance - end of period at Sep. 30, 2015	29,127	7,833		(1,974)	4,665		18,795	1,285	(1,406)	(71)	$ (192)
Balance - beginning of period at Dec. 31, 2015	29,135	7,833		(1,922)	4,481		19,478	874	(1,539)	(70)
Shares Issued for Chubb Corp Acquisition			$ 3,288			11,916
Dividends declared on Common Shares – par value reduction		0
Common Shares repurchased				0
Net shares redeemed under employee share-based compensation plans				372	(365)	$ 323
Exercise of stock options					(44)
Share-based compensation expense and other					250
Funding of dividends declared to Retained earnings					(960)
Net income	2,525						2,525
Funding of dividends declared from Additional paid-in capital							960
Dividends declared on Common Shares							(960)
Change in period, before reclassification from AOCI, net of income tax benefit (expense) of $(559) and $102								1,540
Amounts reclassified from AOCI, net of income tax benefit of $16 and $10								133
Change in period, net of income tax benefit (expense) of $(543) and $112								1,673
Change in period, net of income tax benefit (expense) of $(18) and $35									251
Change in period, net of income tax expense of nil and $(2)										8
Balance - end of period at Sep. 30, 2016	$ 48,372	$ 11,121		$ (1,550)	$ 15,601		$ 22,003	$ 2,547	$ (1,288)	$ (62)	$ 1,197