Acquisitions (Detail) $ / shares in Units, $ in Millions		3 Months Ended
	Jan. 14, 2016 USD ($) $ / shares shares	Mar. 31, 2016 USD ($) shares		Mar. 31, 2015 USD ($) 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		$ 7,955				$ 887
Chubb integration expenses		$ 148		$ 0
Weighted-average shares outstanding | shares		446,739,586		328,212,376
Goodwill		$ 15,404				4,796
Unpaid losses and loss expenses		60,206				37,303
Unearned premiums		14,896				8,439
Insurance and reinsurance balances receivable		7,692				5,323
Cash		1,091	[1],[2]	$ 948	[3]	1,775	[1],[4]			$ 655
Common Shares (CHF 24.15 par value; 479,783,864 and 342,832,412 shares issued; 464,283,520 and 324,563,441 shares outstanding)		11,121				7,833
Investments		97,586				66,251
Accrued investment income		891				513
Reinsurance recoverable on losses and loss expenses		12,891				11,386
Prepaid reinsurance premiums		2,376				2,082
Other assets		5,150				3,821
Insurance and reinsurance balances payable		4,733				4,270
Accounts payable, accrued expenses, and other liabilities		9,050				6,205
Deferred Tax Liabilities, Net		(1,142)				0
Long-term debt		$ (12,636)				$ (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	10,445
Total Consideration	29,846
Unpaid losses and loss expenses	(22,878)
Unearned premiums	(7,016)
Insurance and reinsurance balances receivable	2,948
Cash	57
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	42,869
Accrued investment income	337
Reinsurance recoverable on losses and loss expenses	1,657
Indefinite-Lived Intangible Assets	2,860
Finite-Lived Intangible Assets	4,795
Prepaid reinsurance premiums	280
Other assets	989
Insurance and reinsurance balances payable	(468)
Accounts payable, accrued expenses, and other liabilities	(1,919)
Deferred Tax Liabilities, Net	(1,350)
Long-term debt	(3,760)
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	$ 19,401
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

[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 March 31, 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 March 31, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] 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 March 31, 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.