Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2020		Jun. 30, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 3,697		$ 2,708
Purchases of fixed maturities available for sale	(13,058)		(12,566)
Purchases of fixed maturities held to maturity	(42)		(73)
Purchases of equity securities	(2,824)		(147)
Proceeds From Sale Of Available For Sale Securities Debt Condensed	7,734		7,838
Sales of equity securities	1,353		266
Maturities and redemptions of fixed maturities available for sale	5,220		3,963
Maturities and redemptions of fixed maturities held to maturity	642		598
Net change in short-term investments	173		(763)
Net derivative instruments settlements	(18)		(536)
Private equity contribution	(546)		(920)
Private equity distribution	443		780
Payments for Other Deposits	(1,550)		0
Capital contribution	0		0
Other	(221)		(727)
Net cash flows used for investing activities	(2,694)		(2,287)
Dividends paid on Common Shares	(678)		(671)
Common Shares repurchased	(333)		(741)
Proceeds from Issuance of Long-term Debt	0		1,289
Repayments of Long-term Debt	0		(500)
Proceeds from issuance of repurchase agreements	1,402		1,984
Repayments of repurchase agreements	(1,402)		(1,986)
Proceeds from share-based compensation plans	74		95
Dividend to Parent Company	0		0
Advances (to) from affiliates	0		0
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	215		237
Policyholder contract withdrawals	(173)		(138)
Proceeds from (Payments for) Other Financing Activities	(3)		0
Net cash flows used for financing activities	(898)		(431)
Effect of foreign currency rate changes on cash and restricted cash	(42)		38
Net Increase (Decrease) in cash and restricted cash	63		28
Cash and restricted cash - beginning of period	1,646	[1]	1,340	[2]
Cash and restricted cash - end of period	1,709	[1]	1,368	[2]
Chubb Limited (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	181		323
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	0		0
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	0		0
Net derivative instruments settlements	0		0
Private equity contribution	0		0
Private equity distribution	0		0
Payments for Other Deposits	0
Capital contribution	(1,200)		(600)
Other	(1)		0
Net cash flows used for investing activities	(1,201)		(600)
Dividends paid on Common Shares	(678)		(671)
Common Shares repurchased	(333)		0
Proceeds from Issuance of Long-term Debt			0
Repayments of Long-term Debt			0
Proceeds from issuance of repurchase agreements	0		0
Repayments of repurchase agreements	0		0
Proceeds from share-based compensation plans	0		0
Dividend to Parent Company	0		0
Advances (to) from affiliates	1,149		801
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	882	[1]	142	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities	0		0
Net cash flows used for financing activities	1,020		272
Effect of foreign currency rate changes on cash and restricted cash	(1)		5
Net Increase (Decrease) in cash and restricted cash	(1)		0
Cash and restricted cash - beginning of period	2	[1]	1	[2]
Cash and restricted cash - end of period	1	[1]	1	[2]
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(307)		1,302
Purchases of fixed maturities available for sale	(13)		(5)
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed	7		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	29		16
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	761		(11)
Net derivative instruments settlements	69		(35)
Private equity contribution	0		0
Private equity distribution	0		0
Payments for Other Deposits	0
Capital contribution	0		(110)
Other	(3)		(12)
Net cash flows used for investing activities	850		(157)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from Issuance of Long-term Debt			1,289
Repayments of Long-term Debt			(500)
Proceeds from issuance of repurchase agreements	0		0
Repayments of repurchase agreements	0		0
Proceeds from share-based compensation plans	0		0
Dividend to Parent Company	0		0
Advances (to) from affiliates	(1,168)		(1,498)
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	186	[1]	(437)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities	(3)		0
Net cash flows used for financing activities	(985)		(1,146)
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(442)		(1)
Cash and restricted cash - beginning of period	442	[1]	2	[2]
Cash and restricted cash - end of period	0	[1]	1	[2]
Other Chubb Limited Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	3,933		2,943
Purchases of fixed maturities available for sale	(13,045)		(12,561)
Purchases of fixed maturities held to maturity	(42)		(73)
Purchases of equity securities	(2,824)		(147)
Proceeds From Sale Of Available For Sale Securities Debt Condensed	7,727		7,838
Sales of equity securities	1,353		266
Maturities and redemptions of fixed maturities available for sale	5,191		3,947
Maturities and redemptions of fixed maturities held to maturity	642		598
Net change in short-term investments	(588)		(752)
Net derivative instruments settlements	(87)		(501)
Private equity contribution	(546)		(920)
Private equity distribution	443		780
Payments for Other Deposits	(1,550)
Capital contribution	0		0
Other	(217)		(715)
Net cash flows used for investing activities	(3,543)		(2,240)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		(741)
Proceeds from Issuance of Long-term Debt			0
Repayments of Long-term Debt			0
Proceeds from issuance of repurchase agreements	1,402		1,984
Repayments of repurchase agreements	(1,402)		(1,986)
Proceeds from share-based compensation plans	74		95
Dividend to Parent Company	(110)		(1,860)
Advances (to) from affiliates	19		697
Capital contribution	1,200		710
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	215		237
Policyholder contract withdrawals	(173)		(138)
Proceeds from (Payments for) Other Financing Activities	0		0
Net cash flows used for financing activities	1,225		(1,002)
Effect of foreign currency rate changes on cash and restricted cash	(41)		33
Net Increase (Decrease) in cash and restricted cash	1,574		(266)
Cash and restricted cash - beginning of period	1,202	[1]	1,989	[2]
Cash and restricted cash - end of period	2,776	[1]	1,723	[2]
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(110)		(1,860)
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Proceeds From Sale Of Available For Sale Securities Debt Condensed	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	0		0
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	0		0
Net derivative instruments settlements	0		0
Private equity contribution	0		0
Private equity distribution	0		0
Payments for Other Deposits	0
Capital contribution	1,200		710
Other	0		0
Net cash flows used for investing activities	1,200		710
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from Issuance of Long-term Debt			0
Repayments of Long-term Debt			0
Proceeds from issuance of repurchase agreements	0		0
Repayments of repurchase agreements	0		0
Proceeds from share-based compensation plans	0		0
Dividend to Parent Company	110		1,860
Advances (to) from affiliates	0		0
Capital contribution	(1,200)		(710)
Net proceeds from (payments to) affiliated notional cash pooling program	(1,068)	[1]	295	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities	0		0
Net cash flows used for financing activities	(2,158)		1,445
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(1,068)		295
Cash and restricted cash - beginning of period	0	[1]	(652)	[2]
Cash and restricted cash - end of period	$ (1,068)	[1]	$ (357)	[2]

[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, 2020 and December 31, 2019, 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, 2019 and December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.