Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2019		Sep. 30, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	$ 4,913		$ 3,897
Purchases of fixed maturities available for sale	(19,778)		(16,788)
Purchases of fixed maturities held to maturity	(143)		(380)
Purchases of equity securities	(466)		(148)
Sales of fixed maturities available for sale	10,430		9,041
Proceeds From Sale Of Available For Sale Securities Debt Condensed	10,436
Sales of equity securities	577		247
Maturities and redemptions of fixed maturities available for sale	6,390		5,482
Maturities and redemptions of fixed maturities held to maturity	814		1,001
Net change in short-term investments	202		64
Net derivative instruments settlements	(647)		(46)
Private equity contribution	(1,093)		(1,112)
Private equity distribution	973		743
Capital contribution	0		0
Other	(826)		(231)
Net cash flows used for investing activities	(3,561)		(2,127)
Dividends paid on Common Shares	(1,014)		(1,001)
Common Shares repurchased	(1,203)		(732)
Proceeds from issuance of long-term debt	1,286		2,171
Repayment of long-term debt	(501)		(2,001)
Proceeds from issuance of repurchase agreements	2,394		1,572
Repayments of repurchase agreements	(2,396)		(1,566)
Proceeds from share-based compensation plans	155		86
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	376		269
Policyholder contract withdrawals	(221)		(222)
Net cash flows used for financing activities	(1,124)		(1,424)
Effect of foreign currency rate changes on cash and restricted cash	21		(40)
Net Increase (Decrease) in cash and restricted cash	249		306
Cash and restricted cash - beginning of period	1,340	[1]	851	[2]
Cash and restricted cash - end of period	1,589	[1]	1,157	[2]
Chubb Limited (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	421		237
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	(1,000)		(1,125)
Other	0		0
Net cash flows used for investing activities	(1,000)		(1,125)
Dividends paid on Common Shares	(1,014)		(1,001)
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	996		1,722
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	593	[1]	165	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	575		886
Effect of foreign currency rate changes on cash and restricted cash	5		(1)
Net Increase (Decrease) in cash and restricted cash	1		(3)
Cash and restricted cash - beginning of period	1	[1]	3	[2]
Cash and restricted cash - end of period	2	[1]	0	[2]
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	1,118		4,701
Purchases of fixed maturities available for sale	(16)		(30)
Purchases of fixed maturities held to maturity	0		0
Purchases of equity securities	0		0
Sales of fixed maturities available for sale			6
Proceeds From Sale Of Available For Sale Securities Debt Condensed	1
Sales of equity securities	0		0
Maturities and redemptions of fixed maturities available for sale	18		15
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	(5)		6
Net derivative instruments settlements	(55)		(7)
Private equity contribution	0		0
Private equity distribution	0		0
Capital contribution	(110)		(3,500)
Other	(10)		(18)
Net cash flows used for investing activities	(177)		(3,528)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from issuance of long-term debt	1,286		2,171
Repayment of long-term debt	(500)		(2,000)
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	(1,715)		(1,310)
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	(15)	[1]	(34)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	(944)		(1,173)
Effect of foreign currency rate changes on cash and restricted cash	1		0
Net Increase (Decrease) in cash and restricted cash	(2)		0
Cash and restricted cash - beginning of period	2	[1]	1	[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	5,234		3,797
Purchases of fixed maturities available for sale	(19,762)		(16,758)
Purchases of fixed maturities held to maturity	(143)		(380)
Purchases of equity securities	(466)		(148)
Sales of fixed maturities available for sale			9,035
Proceeds From Sale Of Available For Sale Securities Debt Condensed	10,435
Sales of equity securities	577		247
Maturities and redemptions of fixed maturities available for sale	6,372		5,467
Maturities and redemptions of fixed maturities held to maturity	814		1,001
Net change in short-term investments	207		58
Net derivative instruments settlements	(592)		(39)
Private equity contribution	(1,093)		(1,112)
Private equity distribution	973		743
Capital contribution	0		0
Other	(816)		(213)
Net cash flows used for investing activities	(3,494)		(2,099)
Dividends paid on Common Shares	0		0
Common Shares repurchased	(1,203)		(732)
Proceeds from issuance of long-term debt	0		0
Repayment of long-term debt	(1)		(1)
Proceeds from issuance of repurchase agreements	2,394		1,572
Repayments of repurchase agreements	(2,396)		(1,566)
Proceeds from share-based compensation plans	155		86
Dividend to Parent Company	(1,860)		(4,838)
Advances (to) from affiliates	719		(412)
Capital contribution	1,110		4,625
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	376		269
Policyholder contract withdrawals	(221)		(222)
Net cash flows used for financing activities	(927)		(1,219)
Effect of foreign currency rate changes on cash and restricted cash	15		(39)
Net Increase (Decrease) in cash and restricted cash	828		440
Cash and restricted cash - beginning of period	1,989	[1]	962	[2]
Cash and restricted cash - end of period	2,817	[1]	1,402	[2]
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net Cash Provided by (Used in) Operating Activities	(1,860)		(4,838)
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	1,110		4,625
Other	0		0
Net cash flows used for investing activities	1,110		4,625
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		4,838
Advances (to) from affiliates	0		0
Capital contribution	(1,110)		(4,625)
Net proceeds from (payments to) affiliated notional cash pooling program	(578)	[1]	(131)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows used for financing activities	172		82
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(578)		(131)
Cash and restricted cash - beginning of period	(652)	[1]	(115)	[2]
Cash and restricted cash - end of period	$ (1,230)	[1]	$ (246)	[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 September 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 September 30, 2018 and December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.