Consolidated Statements Of Shareholders' Equity - USD ($) $ in Millions	Total	Common Shares	Common Shares in Treasury	Additional Paid-in Capital	Retained Earnings	Net unrealized appreciation on investments	Cumulative Translation Adjustment	Accumulated Defined Benefit Plans Adjustment [Member]	Accumulated Other Comprehensive Income	The Chubb Corporation [Member] Common Shares	The Chubb Corporation [Member] Additional Paid-in Capital
Balance – beginning of year at Dec. 31, 2013		$ 8,899	$ (255)	$ 5,238	$ 13,791	$ 1,174	$ 63	$ (85)
Dividends declared on Common Shares – par value reduction		(844)
Common Shares repurchased			(1,449)
Net shares redeemed under employee share-based compensation plans			256	(167)
Stock Issued During Period, Value, Stock Options Exercised				(58)
Share-based compensation expense and other				185
Funding of dividends declared from Additional paid-in capital				(81)	81
Tax benefit on share-based compensation expense				28
Net income	$ 2,853				2,853
Dividends declared on Common Shares					(81)
Change in year, before reclassification from AOCI, net of income tax benefit (expense) of $72, $154, and $(176)						644
Amounts reclassified from AOCI, net of income tax benefit (expense) of $28, $(2), and $9						33
Change in year, net of income tax benefit (expense) of $100, $152, and $(167)						677
Change in year, net of income tax benefit (expense) of $30, nil, and $(12)							(644)
Change in year, net of income tax benefit (expense) of $(184), $(6), and $4								6
Balance – Ending of year at Dec. 31, 2014	29,587	8,055	(1,448)	5,145	16,644	1,851	(581)	(79)	$ 1,191
Dividends declared on Common Shares – par value reduction		(222)
Common Shares repurchased			(734)
Shares issued for Chubb Corp acquisition											$ 0
Net shares redeemed under employee share-based compensation plans			260	(160)
Stock Issued During Period, Value, Stock Options Exercised				(61)
Share-based compensation expense and other				184
Funding of dividends declared from Additional paid-in capital				(653)	653
Tax benefit on share-based compensation expense				26
Net income	2,834				2,834
Dividends declared on Common Shares					(653)
Change in year, before reclassification from AOCI, net of income tax benefit (expense) of $72, $154, and $(176)						(1,126)
Amounts reclassified from AOCI, net of income tax benefit (expense) of $28, $(2), and $9						149
Change in year, net of income tax benefit (expense) of $100, $152, and $(167)						(977)
Change in year, net of income tax benefit (expense) of $30, nil, and $(12)							(958)
Change in year, net of income tax benefit (expense) of $(184), $(6), and $4								9
Balance – Ending of year at Dec. 31, 2015	29,135	7,833	(1,922)	4,481	19,478	874	(1,539)	(70)	(735)
Common Shares repurchased			0
Shares issued for Chubb Corp acquisition										$ 3,288	11,916
Net shares redeemed under employee share-based compensation plans			442	(382)							$ 323
Stock Issued During Period, Value, Stock Options Exercised				(64)
Share-based compensation expense and other				313
Funding of dividends declared from Additional paid-in capital				(1,284)	1,284
Tax benefit on share-based compensation expense				32
Net income	4,135				4,135
Dividends declared on Common Shares					(1,284)
Change in year, before reclassification from AOCI, net of income tax benefit (expense) of $72, $154, and $(176)						37
Amounts reclassified from AOCI, net of income tax benefit (expense) of $28, $(2), and $9						147
Change in year, net of income tax benefit (expense) of $100, $152, and $(167)						184
Change in year, net of income tax benefit (expense) of $30, nil, and $(12)							(124)
Change in year, net of income tax benefit (expense) of $(184), $(6), and $4								361
Balance – Ending of year at Dec. 31, 2016	$ 48,275	$ 11,121	$ (1,480)	$ 15,335	$ 23,613	$ 1,058	$ (1,663)	$ 291	$ (314)