Acquisitions (Detail) $ / shares in Units, $ in Millions				12 Months Ended
	Jan. 14, 2016 USD ($) $ / shares shares	Oct. 31, 2014 USD ($)	Jun. 17, 2014 USD ($)	Dec. 31, 2016 USD ($)		Dec. 31, 2016 USD ($) $ / shares shares		Dec. 31, 2015 USD ($) $ / shares shares		Dec. 31, 2014 USD ($) shares		Apr. 01, 2015 USD ($)	Apr. 28, 2014 USD ($)	Dec. 31, 2013 USD ($)
Business Acquisition [Line Items]
Weighted Average Number of Shares Outstanding, Basic | shares						462,519,789		325,589,361		335,609,899
Cash				$ 985	[1],[2]	$ 985	[1],[2]	$ 1,775	[1],[3],[4]	$ 655	[1],[5]			$ 579	[5]
Investments				99,094		99,094		66,251
Accrued investment income				918		918		513
Insurance and reinsurance balances receivable				8,970		8,970		5,323
Reinsurance recoverable on paid losses and loss expenses				13,577		13,577		11,386
Prepaid reinsurance premiums				2,448		2,448		2,082
Other assets				5,090		5,090		3,821
Unpaid losses and loss expenses				(60,540)		(60,540)		(37,303)		(38,315)				$ (37,443)
Unearned premiums				(14,779)		(14,779)		(8,439)
Reinsurance Payable				(5,637)		(5,637)		(4,270)
Accounts Payable, Accrued Expenses and Other Liabilities				(8,617)		(8,617)		(6,205)
Deferred Tax Liabilities, Net				(988)		(988)
Long-term Debt				(12,610)		(12,610)		(9,389)
Intangible Assets, Net (Excluding Goodwill)				6,763		6,763		887
Goodwill				15,332		15,332		4,796		$ 4,904
Common Shares				11,121		11,121		7,833
Large Corporate Property And Casualty Business Of Itau Seguros [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		$ 606
Finite lived intangible assets		60
Goodwill		$ 445
Fireman's Fund high net worth personal lines [Member]
Business Acquisition [Line Items]
Business Acquisition, Financing Of Acquisition With Cash												$ 365
Cash												629
Insurance and reinsurance balances receivable												124
Unpaid losses and loss expenses												(417)
Unearned premiums												(428)
Fair Value of Assets Acquired												753
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities												863
Intangible Assets, Net (Excluding Goodwill)												278
Goodwill												$ 196
The Siam Commercial Sammagi Insurance PCL (Samaggi)
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross			$ 176
Finite lived intangible assets													$ 80
Total ownership percentage acquired			93.03%
Additional investment percentage to be acquired after tender offer			32.17%										60.86%
Goodwill													$ 46
The Chubb Corporation [Member]
Business Acquisition [Line Items]
Total Value of Equity Awards Issued in Acquisition	$ 525
Purchase Price	29,500
Business Acquisition, Financing Of Acquisition With Cash	9,000
Senior notes issued to finance acquisition	$ 5,300
Weighted Average Number of Shares Outstanding, Basic | shares	228,000,000
Shares Conversion Ratio in Acquisition	0.6019
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	137,000,000
Share Price | $ / shares	$ 111.02
Equity Issued in Business Combination, Fair Value Disclosure	$ 15,204
Business Acquisition, Share Price | $ / shares	$ 62.93
Payments to Acquire Businesses, Gross	$ 14,319
Attributed Value Equity Awards Assumed in Acquisition	323
Business Combination, Consideration Transferred	29,846
Cash	71
Investments	42,967
Accrued investment income	359
Insurance and reinsurance balances receivable	3,095
Reinsurance recoverable on paid losses and loss expenses	1,676
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Indefinite-Lived Intangible Assets	2,860
Finite lived intangible assets	4,795
Prepaid reinsurance premiums	280
Other assets	853
Unpaid losses and loss expenses	(22,923)
Unearned premiums	(7,011)
Reinsurance Payable	(603)
Accounts Payable, Accrued Expenses and Other Liabilities	(2,030)
Deferred Tax Liabilities, Net	(1,292)
Long-term Debt	(3,765)
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	19,332
Goodwill	10,514
Goodwill, Expected Tax Deductible Amount	$ 0
Chubb Corp, Revenue since acquisition date				12,376
Chubb Corp, Earnings since acquisition date				$ 1,756
Chubb Corp, Pro Forma Revenue						31,937		32,622
Chubb Corp, Pro Forma Net Income (Loss)						$ 4,183		$ 4,478
Chubb Corp, Pro Forma Earnings Per Share, Basic | $ / shares						$ 8.95		$ 9.61
Chubb Corp, Pro Forma Earnings Per Share, Diluted | $ / shares						$ 8.88		$ 9.52

[1] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2016 and 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. Refer to Note 1 f) for additional information. At December 31, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2015 and 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. Refer to Note 1 f) for additional information. At December 31, 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[5] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2014 and 2013, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.