Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions	6 Months Ended
	Jun. 30, 2019		Jun. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	$ 2,708		$ 2,197
Purchases of fixed maturities available for sale	(12,566)		(12,297)
Purchases of fixed maturities held to maturity	(73)		(337)
Purchases of equity securities	(147)		(85)
Sales of fixed maturities available for sale	7,832		6,858
Proceeds From Sale Of Available For Sale Securities Debt Condensed	7,838
Sales of equity securities	266		83
Maturities and redemptions of fixed maturities available for sale	3,963		3,920
Maturities and redemptions of fixed maturities held to maturity	598		732
Net change in short-term investments	(763)		401
Net derivative instruments settlements	(536)		5
Private equity contribution	(920)		(813)
Private equity distribution	780		413
Capital contribution	0		0
Other	(727)		(140)
Net cash flows used for investing activities	(2,287)		(1,260)
Dividends paid on Common Shares	(671)		(661)
Common Shares repurchased	(741)		(347)
Proceeds from issuance of long-term debt	1,289		2,171
Repayment of long-term debt	(500)		(1,900)
Proceeds from issuance of repurchase agreements	1,984		1,014
Repayments of repurchase agreements	(1,986)		(1,009)
Proceeds from share-based compensation plans	95		60
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		0
Policyholder contract deposits	237		192
Policyholder contract withdrawals	(138)		(169)
Net cash flows used for financing activities	(431)		(649)
Effect of foreign currency rate changes on cash and restricted cash	38		(38)
Net Increase (Decrease) in cash and restricted cash	28		250
Cash and restricted cash - beginning of period	1,340		851
Cash and restricted cash - end of period	1,368		1,101
Chubb Limited (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	323		43
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale	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
Capital contribution	(600)		(750)
Other	0		0
Net cash flows used for investing activities	(600)		(750)
Dividends paid on Common Shares	(671)		(661)
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	0		0
Repayment of long-term debt	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	801		963
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	142	[1]	403	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	272		705
Effect of foreign currency rate changes on cash and restricted cash	5		0
Net Increase (Decrease) in cash and restricted cash	0		(2)
Cash and restricted cash - beginning of period	1	[1]	3	[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 flows from operating activities	1,302		3,042
Purchases of fixed maturities available for sale	(5)		(22)
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale	0		0
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	16		14
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	(11)		6
Net derivative instruments settlements	(35)		(8)
Private equity contribution	0		0
Private equity distribution	0		0
Capital contribution	(110)		(3,500)
Other	(12)		(7)
Net cash flows used for investing activities	(157)		(3,517)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	1,289		2,171
Repayment of long-term debt	(500)		(1,900)
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	(1,498)		(518)
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	(437)	[1]	722	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	(1,146)		475
Effect of foreign currency rate changes on cash and restricted cash	0		0
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]
Other Chubb Limited Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	2,943		2,187
Purchases of fixed maturities available for sale	(12,561)		(12,275)
Purchases of fixed maturities held to maturity	(73)		(337)
Purchases of equity securities	(147)		(85)
Sales of fixed maturities available for sale			6,858
Proceeds From Sale Of Available For Sale Securities Debt Condensed	7,838
Sales of equity securities	266		83
Maturities and redemptions of fixed maturities available for sale	3,947		3,906
Maturities and redemptions of fixed maturities held to maturity	598		732
Net change in short-term investments	(752)		395
Net derivative instruments settlements	(501)		13
Private equity contribution	(920)		(813)
Private equity distribution	780		413
Capital contribution	0		0
Other	(715)		(133)
Net cash flows used for investing activities	(2,240)		(1,243)
Dividends paid on Common Shares	0		0
Common Shares repurchased	(741)		(347)
Proceeds from issuance of long-term debt	0		0
Repayment of long-term debt	0		0
Proceeds from issuance of repurchase agreements	1,984		1,014
Repayments of repurchase agreements	(1,986)		(1,009)
Proceeds from share-based compensation plans	95		60
Dividend to Parent Company	(1,860)		(3,075)
Advances (to) from affiliates	697		(445)
Capital contribution	710		4,250
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	237		192
Policyholder contract withdrawals	(138)		(169)
Net cash flows used for financing activities	(1,002)		471
Effect of foreign currency rate changes on cash and restricted cash	33		(38)
Net Increase (Decrease) in cash and restricted cash	(266)		1,377
Cash and restricted cash - beginning of period	1,989	[1]	962	[2]
Cash and restricted cash - end of period	1,723	[1]	2,339	[2]
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	(1,860)		(3,075)
Purchases of fixed maturities available for sale	0		0
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale			0
Proceeds From Sale Of Available For Sale Securities Debt Condensed	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
Capital contribution	710		4,250
Other	0		0
Net cash flows used for investing activities	710		4,250
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	0		0
Repayment of long-term debt	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	1,860		3,075
Advances (to) from affiliates	0		0
Capital contribution	(710)		(4,250)
Net proceeds from (payments to) affiliated notional cash pooling program	295	[1]	(1,125)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	1,445		(2,300)
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	295		(1,125)
Cash and restricted cash - beginning of period	(652)	[1]	(115)	[2]
Cash and restricted cash - end of period	$ (357)	[1]	$ (1,240)	[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, 2019 and December 31, 2018, 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, 2018 and December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.