Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2016	[3]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Cash Acquired from Acquisition		$ 45		$ 0		$ 0
Net cash flows from operating activities		6,342		5,480		4,503
Payments To Acquire Available For Sale Securities Debt Condensed		(25,846)		(24,735)		(25,747)
Purchases of fixed maturities held to maturity		(229)		(456)		(352)
Purchases of equity securities		(531)		(207)		(173)
Proceeds From Sale Of Available For Sale Securities Debt Condensed		13,116		14,030		13,255
Sales of equity securities		611		315		187
Maturities and redemptions of fixed maturities available for sale		9,039		7,352		10,425
Maturities and redemptions of fixed maturities held to maturity		946		1,124		879
Net change in short-term investments		(1,117)		516		(537)
Net derivative instruments settlements		(703)		16		(265)
Private equity contributions		(1,315)		(1,337)		(648)
Private equity distributions		1,390		980		1,084
Payments to Acquire Businesses, Net of Cash Acquired		(29)		0		0
Payment Of Contributions To Subsidiary		0		0
Other		(1,237)		(533)		(530)
Net Cash Provided by (Used in) Investing Activities		(5,905)		(2,935)		(2,422)
Dividends paid on Common Shares		(1,354)		(1,337)		(1,308)
Common Shares repurchased		(1,530)		(1,044)		(801)
Proceeds from issuance of long-term debt		2,828		2,171		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		2,817		2,029		2,353
Repayments of Long-term Debt		(510)		(2,001)		(501)
Payments for Securities Purchased under Agreements to Resell		(2,817)		(2,019)		(2,348)
Proceeds from share-based compensation plans		204		115		151
Advances from (to) affiliates		0		0		0
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0		0
Net proceeds from (Repayments to) affiliated notional cash pooling program		0		0	[1]	0
Policyholder contract deposits		514		453		442
Policyholder contract withdrawals		(303)		(358)		(307)
Net cash flows (used for) from financing activities		(151)		(1,991)		(2,319)
Effect of foreign currency rate changes on cash and restricted cash		20		(65)		1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		306		489		(237)
Cash and restricted cash		1,646	[2]	1,340	[1],[2]	851	[2],[3]	$ 1,088
Parent Company Only
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities	[4]	412		256		781
Payments To Acquire Available For Sale Securities Debt Condensed		0		0		0
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		0		0		0
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		0		0		0
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		0		0		0
Net derivative instruments settlements		0		0		0
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment Of Contributions To Subsidiary		(1,000)		(1,475)
Other		0		0		0
Net Cash Provided by (Used in) Investing Activities		(1,000)		(1,475)		0
Dividends paid on Common Shares		(1,354)		(1,337)		(1,308)
Common Shares repurchased		(327)		0		0
Proceeds from issuance of long-term debt		0		0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		0		0		0
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		2,301		2,519		892
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0
Net proceeds from (Repayments to) affiliated notional cash pooling program	[5]	(35)		35		(363)
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Net cash flows (used for) from financing activities		585		1,217		(779)
Effect of foreign currency rate changes on cash and restricted cash		4		0		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		1		(2)		2
Cash and restricted cash		2	[2]	1	[1],[2]	3	[2],[3]	1
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		2,926		4,654		1,648
Payments To Acquire Available For Sale Securities Debt Condensed		(21)		(38)		(9)
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		1		11		99
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		41		17		29
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		(808)		3		189
Net derivative instruments settlements		(74)		(7)		(15)
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment Of Contributions To Subsidiary		(110)		(3,550)
Other		(4)		(18)		(10)
Net Cash Provided by (Used in) Investing Activities		(975)		(3,582)		283
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		0		0		0
Proceeds from issuance of long-term debt		2,828		2,171
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		(500)		(2,000)		(500)
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		(3,223)		(1,744)		(927)
Dividends to parent company		0		0		0
Proceeds from Contributions from Parent		0
Net proceeds from (Repayments to) affiliated notional cash pooling program		(617)		502		(504)
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Net cash flows (used for) from financing activities		(1,512)		(1,071)		(1,931)
Effect of foreign currency rate changes on cash and restricted cash		1		0		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		440		1		0
Cash and restricted cash		442	[2]	2	[1],[2]	1	[2],[3]	1
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		6,878		5,878		4,598
Payments To Acquire Available For Sale Securities Debt Condensed		(25,825)		(24,697)		(25,738)
Purchases of fixed maturities held to maturity		(229)		(456)		(352)
Purchases of equity securities		(531)		(207)		(173)
Proceeds From Sale Of Available For Sale Securities Debt Condensed		13,115		14,019		13,156
Sales of equity securities		611		315		187
Maturities and redemptions of fixed maturities available for sale		8,998		7,335		10,396
Maturities and redemptions of fixed maturities held to maturity		946		1,124		879
Net change in short-term investments		(309)		513		(726)
Net derivative instruments settlements		(629)		23		(250)
Private equity contributions		(1,315)		(1,337)		(648)
Private equity distributions		1,390		980		1,084
Payments to Acquire Businesses, Net of Cash Acquired		(29)
Other		(1,233)		(515)		(520)
Net Cash Provided by (Used in) Investing Activities		(5,040)		(2,903)		(2,705)
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		(1,203)		(1,044)		(801)
Proceeds from issuance of long-term debt		0		0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		2,817		2,029		2,353
Repayments of Long-term Debt		(10)		(1)		(1)
Payments for Securities Purchased under Agreements to Resell		(2,817)		(2,019)		(2,348)
Proceeds from share-based compensation plans		204		115		151
Advances from (to) affiliates		922		(775)		35
Dividends to parent company		(3,874)		(5,308)		(2,524)
Proceeds from Contributions from Parent		1,110		5,025
Net proceeds from (Repayments to) affiliated notional cash pooling program		0		0		0
Policyholder contract deposits		514		453		442
Policyholder contract withdrawals		(303)		(358)		(307)
Net cash flows (used for) from financing activities		(2,640)		(1,883)		(3,000)
Effect of foreign currency rate changes on cash and restricted cash		15		(65)		1
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		(787)		1,027		(1,106)
Cash and restricted cash		1,202	[2]	1,989	[1],[2]	962	[3]	2,068
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Net cash flows from operating activities		(3,874)		(5,308)		(2,524)
Payments To Acquire Available For Sale Securities Debt Condensed		0		0		0
Purchases of fixed maturities held to maturity		0		0		0
Purchases of equity securities		0		0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed		0		0		0
Sales of equity securities		0		0		0
Maturities and redemptions of fixed maturities available for sale		0		0		0
Maturities and redemptions of fixed maturities held to maturity		0		0		0
Net change in short-term investments		0		0		0
Net derivative instruments settlements		0		0		0
Private equity contributions		0		0		0
Private equity distributions		0		0		0
Payment Of Contributions To Subsidiary		1,110		5,025
Other		0		0		0
Net Cash Provided by (Used in) Investing Activities		1,110		5,025		0
Dividends paid on Common Shares		0		0		0
Common Shares repurchased		0		0		0
Proceeds from issuance of long-term debt				0		0
Proceeds from (Payments for) in Securities Sold under Agreements to Repurchase		0		0		0
Repayments of Long-term Debt		0		0		0
Payments for Securities Purchased under Agreements to Resell		0		0		0
Proceeds from share-based compensation plans		0		0		0
Advances from (to) affiliates		0		0		0
Dividends to parent company		3,874		5,308		2,524
Proceeds from Contributions from Parent		(1,110)		(5,025)
Net proceeds from (Repayments to) affiliated notional cash pooling program		652		(537)	[1]	867
Policyholder contract deposits		0		0		0
Policyholder contract withdrawals		0		0		0
Net cash flows (used for) from financing activities		3,416		(254)		3,391
Effect of foreign currency rate changes on cash and restricted cash		0		0		0
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect		$ 652		(537)		867
Cash and restricted cash				$ (652)	[1],[2]	$ (115)	[2],[3]	$ (982)

[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, 2018 and 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] 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, 2018, 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, 2017 and 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] Includes cash dividends received from subsidiaries of $200 million, $75 million, and $450 million in 2019, 2018, and 2017, respectively.

[5] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.