Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Common Stock [Member] The Chubb Corporation [Member]	Treasury Stock [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]	Accumulated Translation Adjustment [Member]	Accumulated Defined Benefit Plans 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				143	(153)	$ 0
Shares Issued for Chubb Corp Acquisition			$ 0			0
Common Shares repurchased				(340)
Exercise of stock options					(18)
Share-based compensation expense and other					63
Funding of dividends declared to Retained earnings					0
Net income	$ 681						681
Funding of dividends declared from Additional paid-in capital							0
Dividends declared on Common Shares							0
Change in period, before reclassification from AOCI, net of income tax expense of $(232) and $(87)								354
Amounts reclassified from AOCI, net of income tax benefit (expense) of $(1) and $4								7
Change in period, net of income tax expense of $(233) and $(83)								361
Change in period, net of income tax benefit (expense) of $(35) and $11									(410)
Change in period, net of income tax benefit (expense) of $(1) and $(3)										10
Balance - end of period at Mar. 31, 2015	29,702	7,833		(1,645)	5,037		17,325	2,212	(991)	(69)	$ 1,152
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				274	(310)	323
Shares Issued for Chubb Corp Acquisition			$ 3,288			$ 11,916
Common Shares repurchased				0
Exercise of stock options					(21)
Share-based compensation expense and other					65
Funding of dividends declared to Retained earnings					(314)
Net income	439						439
Funding of dividends declared from Additional paid-in capital							314
Dividends declared on Common Shares							(314)
Change in period, before reclassification from AOCI, net of income tax expense of $(232) and $(87)								673
Amounts reclassified from AOCI, net of income tax benefit (expense) of $(1) and $4								151
Change in period, net of income tax expense of $(233) and $(83)								824
Change in period, net of income tax benefit (expense) of $(35) and $11									277
Change in period, net of income tax benefit (expense) of $(1) and $(3)										1
Balance - end of period at Mar. 31, 2016	$ 45,897	$ 11,121		$ (1,648)	$ 16,140		$ 19,917	$ 1,698	$ (1,262)	$ (69)	$ 367