Acquisitions (Detail) $ / shares in Units, $ in Millions		3 Months Ended				6 Months Ended
	Jan. 14, 2016 USD ($) $ / shares shares	Jun. 30, 2016 USD ($) shares		Jun. 30, 2015 USD ($) shares		Jun. 30, 2016 USD ($) shares		Jun. 30, 2015 USD ($) shares		Dec. 31, 2015 USD ($)		Nov. 01, 2015 USD ($)	Apr. 01, 2015 USD ($)	Dec. 31, 2014 USD ($)	[3]
Business Acquisition [Line Items]
Other intangible assets		$ 7,398				$ 7,398				$ 887
Chubb integration expenses		$ 98		$ 0		$ 246		$ 0
Weighted-average shares outstanding | shares		467,701,328		325,463,196		457,102,802		326,795,838
Goodwill		$ 15,525				$ 15,525				4,796
Unpaid losses and loss expenses		(60,819)				(60,819)				(37,303)
Unearned premiums		(15,229)				(15,229)				(8,439)
Insurance and reinsurance balances receivable		8,532				8,532				5,323
Cash		1,011	[1],[2]	$ 790	[3]	1,011	[1],[2]	$ 790	[3]	1,775	[1],[4]			$ 655
Common Shares (CHF 24.15 par value; 479,783,864 and 342,832,412 shares issued; 465,012,980 and 324,563,441 shares outstanding)		11,121				11,121				7,833
Investments		99,846				99,846				66,251
Accrued investment income		919				919				513
Reinsurance recoverable on losses and loss expenses		13,235				13,235				11,386
Prepaid reinsurance premiums		2,464				2,464				2,082
Other assets		4,945				4,945				3,821
Insurance and reinsurance balances payable		(4,944)				(4,944)				(4,270)
Accounts payable, accrued expenses, and other liabilities		(9,614)				(9,614)				(6,205)
Long-term debt		$ (12,631)				$ (12,631)				$ (9,389)
The Chubb Corporation [Member]
Business Acquisition [Line Items]
Weighted-average shares outstanding | shares	228,000,000
Business Acquisition, Expected Financing Of Acquisition With Cash	$ 9,000
Goodwill	10,526
Total Consideration	29,846
Unpaid losses and loss expenses	(22,906)
Unearned premiums	(7,033)
Insurance and reinsurance balances receivable	2,981
Cash	71
Expected purchase price	$ 29,500
Approximate number of shares to be issued | shares	323,000,000
Senior notes issued to finance acquisition												$ 5,300
Payments to Acquire Businesses, Gross	$ 14,319
Investments	42,967
Accrued investment income	337
Reinsurance recoverable on losses and loss expenses	1,650
Indefinite-Lived Intangible Assets	2,860
Finite-Lived Intangible Assets	4,795
Prepaid reinsurance premiums	280
Other assets	863
Insurance and reinsurance balances payable	(511)
Accounts payable, accrued expenses, and other liabilities	(1,935)
Deferred Tax Liabilities, Net	(1,334)
Long-term debt	(3,765)
Attributed Value Equity Awards Assumed in Acquisition	323
Total Value of Equity Awards Issued in Acquisition	$ 525
Cash consideration per share | $ / shares	$ 62.93
Fair value of common shares issued by Chubb Limited to common shareholders of Chubb Corp	$ 15,204
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	137,000,000
Share Price | $ / shares	$ 111.02
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 19,320
Shares Conversion Ratio in Acquisition	0.6019
Fireman's Fund high net worth personal lines [Member]
Business Acquisition [Line Items]
Other intangible assets													$ 278
Goodwill													196
Purchase price													365
Assumed liabilities fair value													863
Unpaid losses and loss expenses													(417)
Unearned premiums													(428)
Insurance and reinsurance balances receivable													124
Cash													629
Acquired assets fair value													$ 753
Minimum [Member]
Business Acquisition [Line Items]
Estimated Useful Life						1 year
Maximum [Member]
Business Acquisition [Line Items]
Estimated Useful Life						24 years

[1] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At June 30, 2016 and December 31, 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At June 30, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At June 30, 2015 and December 31, 2014, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At December 31, 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.