Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020		Mar. 31, 2019
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 1,712		$ 1,322
Purchases of fixed maturities available for sale	(6,474)		(5,561)
Purchases of fixed maturities held to maturity	(6)		(1)
Purchases of equity securities	(1,380)		(49)
Proceeds From Sale Of Available For Sale Securities Debt Condensed	4,687		3,293
Sales of equity securities	131		60
Maturities and redemptions of fixed maturities available for sale	2,756		1,831
Maturities and redemptions of fixed maturities held to maturity	440		280
Net change in short-term investments	552		(39)
Net derivative instruments settlements	109		(358)
Private equity contribution	(361)		(410)
Private equity distribution	211		368
Payments for Other Deposits	1,550		0
Capital contribution	0		0
Other	(125)		(87)
Net cash flows used for investing activities	(1,010)		(673)
Dividends paid on Common Shares	(339)		(336)
Common Shares repurchased	(323)		(367)
Proceeds from issuance of repurchase agreements	952		471
Repayments of repurchase agreements	(952)		(470)
Proceeds from share-based compensation plans	47		35
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	135		115
Policyholder contract withdrawals	(162)		(78)
Proceeds from (Payments for) Other Financing Activities	(3)		0
Net cash flows used for financing activities	(645)		(630)
Effect of foreign currency rate changes on cash and restricted cash	(45)		34
Net Increase (Decrease) in cash and restricted cash	12		53
Cash and restricted cash - beginning of period	1,646	[1]	1,340	[2]
Cash and restricted cash - end of period	1,658	[1]	1,393	[2]
Chubb Limited (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	65		307
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)		0
Other	0		0
Net cash flows used for investing activities	(1,200)		0
Dividends paid on Common Shares	(339)		(336)
Common Shares repurchased	(323)		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	1,066		(266)
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	740	[1]	296	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities	0
Net cash flows used for financing activities	1,144		(306)
Effect of foreign currency rate changes on cash and restricted cash	(1)		0
Net Increase (Decrease) in cash and restricted cash	8		1
Cash and restricted cash - beginning of period	2	[1]	1	[2]
Cash and restricted cash - end of period	10	[1]	2	[2]
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(148)		(163)
Purchases of fixed maturities available for sale	(11)		(3)
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	15		6
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	781		(3)
Net derivative instruments settlements	78		(28)
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	860		(150)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		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	(1,102)		308
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	74	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities	(3)
Net cash flows used for financing activities	(1,105)		382
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(393)		69
Cash and restricted cash - beginning of period	442	[1]	2	[2]
Cash and restricted cash - end of period	49	[1]	71	[2]
Other Chubb Limited Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	1,795		1,378
Purchases of fixed maturities available for sale	(6,463)		(5,558)
Purchases of fixed maturities held to maturity	(6)		(1)
Purchases of equity securities	(1,380)		(49)
Proceeds From Sale Of Available For Sale Securities Debt Condensed	4,687		3,293
Sales of equity securities	131		60
Maturities and redemptions of fixed maturities available for sale	2,741		1,825
Maturities and redemptions of fixed maturities held to maturity	440		280
Net change in short-term investments	(229)		(36)
Net derivative instruments settlements	31		(330)
Private equity contribution	(361)		(410)
Private equity distribution	211		368
Payments for Other Deposits	1,550
Capital contribution	0		0
Other	(122)		(75)
Net cash flows used for investing activities	(1,870)		(633)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		(367)
Proceeds from issuance of repurchase agreements	952		471
Repayments of repurchase agreements	(952)		(470)
Proceeds from share-based compensation plans	47		35
Dividend to Parent Company	0		(200)
Advances (to) from affiliates	36		(42)
Capital contribution	1,200		110
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	135		115
Policyholder contract withdrawals	(162)		(78)
Proceeds from (Payments for) Other Financing Activities	0
Net cash flows used for financing activities	1,256		(426)
Effect of foreign currency rate changes on cash and restricted cash	(44)		34
Net Increase (Decrease) in cash and restricted cash	1,137		353
Cash and restricted cash - beginning of period	1,202	[1]	1,989	[2]
Cash and restricted cash - end of period	2,339	[1]	2,342	[2]
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	0		(200)
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		110
Other	0		0
Net cash flows used for investing activities	1,200		110
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		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		200
Advances (to) from affiliates	0		0
Capital contribution	(1,200)		(110)
Net proceeds from (payments to) affiliated notional cash pooling program	(740)	[1]	(370)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Proceeds from (Payments for) Other Financing Activities
Net cash flows used for financing activities	(1,940)		(280)
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(740)		(370)
Cash and restricted cash - beginning of period	0	[1]	(652)	[2]
Cash and restricted cash - end of period	$ (740)	[1]	$ (1,022)	[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 March 31, 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 March 31, 2019 and December 31, 2018, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.