Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Statement Of Cash Flows) (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019		Mar. 31, 2018
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	$ 1,322		$ 551
Purchases of fixed maturities available for sale	(5,561)		(5,972)
Purchases of fixed maturities held to maturity	(1)		(162)
Purchases of equity securities	(49)		(55)
Sales of fixed maturities available for sale	3,287		2,562
Proceeds From Sale Of Available For Sale Securities Debt Condensed	3,293
Sales of equity securities	60		40
Maturities and redemptions of fixed maturities available for sale	1,831		1,865
Maturities and redemptions of fixed maturities held to maturity	280		255
Net change in short-term investments	(39)		731
Net derivative instruments settlements	(358)		39
Private equity contribution	(410)		(353)
Private equity distribution	368		201
Capital contribution	0		0
Other	(87)		(32)
Net cash flows used for investing activities	(673)		(881)
Dividends paid on Common Shares	(336)		(330)
Common Shares repurchased	(367)		(29)
Proceeds from Issuance of Long-term Debt	0		2,175
Proceeds from issuance of long-term debt	0		(300)
Proceeds from issuance of repurchase agreements	471		408
Repayments of repurchase agreements	(470)		(404)
Proceeds from share-based compensation plans	35		34
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	115		118
Policyholder contract withdrawals	(78)		(105)
Net cash flows (used for) from financing activities	(630)		1,567
Effect of foreign currency rate changes on cash and restricted cash	34		25
Net Increase (Decrease) in cash and restricted cash	53		1,262
Cash and Restricted Cash - Beginning of year	1,340		851
Cash and Restricted Cash - end of Year	1,393		2,113
Chubb Limited (Parent Guarantor)
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	307		24
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	0		(750)
Other	0		0
Net cash flows used for investing activities	0		(750)
Dividends paid on Common Shares	(336)		(330)
Common Shares repurchased	0		0
Proceeds from Issuance of Long-term Debt			0
Proceeds from issuance 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	(266)		656
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	296	[1]	400	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows (used for) from financing activities	(306)		726
Effect of foreign currency rate changes on cash and restricted cash	0		(2)
Net Increase (Decrease) in cash and restricted cash	1		(2)
Cash and Restricted Cash - Beginning of year	1		3
Cash and Restricted Cash - end of Year	2		1
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	(163)		2,727
Purchases of fixed maturities available for sale	(3)		(8)
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	6		3
Maturities and redemptions of fixed maturities held to maturity	0		0
Net change in short-term investments	(3)		(14)
Net derivative instruments settlements	(28)		(7)
Private equity contribution	0		0
Private equity distribution	0		0
Capital contribution	(110)		(3,500)
Other	(12)		(3)
Net cash flows used for investing activities	(150)		(3,529)
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from Issuance of Long-term Debt			2,175
Proceeds from issuance of long-term debt			(300)
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	308		(95)
Capital contribution	0		0
Net proceeds from (payments to) affiliated notional cash pooling program	74	[1]	(115)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows (used for) from financing activities	382		1,665
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	69		863
Cash and Restricted Cash - Beginning of year	2		1
Cash and Restricted Cash - end of Year	71		864
Other Chubb Limited Subsidiaries
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	1,378		800
Purchases of fixed maturities available for sale	(5,558)		(5,964)
Purchases of fixed maturities held to maturity	(1)		(162)
Purchases of equity securities	(49)		(55)
Sales of fixed maturities available for sale			2,562
Proceeds From Sale Of Available For Sale Securities Debt Condensed	3,293
Sales of equity securities	60		40
Maturities and redemptions of fixed maturities available for sale	1,825		1,862
Maturities and redemptions of fixed maturities held to maturity	280		255
Net change in short-term investments	(36)		745
Net derivative instruments settlements	(330)		46
Private equity contribution	(410)		(353)
Private equity distribution	368		201
Capital contribution	0		0
Other	(75)		(29)
Net cash flows used for investing activities	(633)		(852)
Dividends paid on Common Shares	0		0
Common Shares repurchased	(367)		(29)
Proceeds from Issuance of Long-term Debt			0
Proceeds from issuance of long-term debt			0
Proceeds from issuance of repurchase agreements	471		408
Repayments of repurchase agreements	(470)		(404)
Proceeds from share-based compensation plans	35		34
Dividend to Parent Company	(200)		(3,000)
Advances (to) from affiliates	(42)		(561)
Capital contribution	110		4,250
Net proceeds from (payments to) affiliated notional cash pooling program	0	[1]	0	[2]
Policyholder contract deposits	115		118
Policyholder contract withdrawals	(78)		(105)
Net cash flows (used for) from financing activities	(426)		711
Effect of foreign currency rate changes on cash and restricted cash	34		27
Net Increase (Decrease) in cash and restricted cash	353		686
Cash and Restricted Cash - Beginning of year	1,989		962
Cash and Restricted Cash - end of Year	2,342		1,648
Consolidation, Eliminations [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Net cash flows from operating activities	(200)		(3,000)
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	110		4,250
Other	0		0
Net cash flows used for investing activities	110		4,250
Dividends paid on Common Shares	0		0
Common Shares repurchased	0		0
Proceeds from Issuance of Long-term Debt			0
Proceeds from issuance 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	200		3,000
Advances (to) from affiliates	0		0
Capital contribution	(110)		(4,250)
Net proceeds from (payments to) affiliated notional cash pooling program	(370)	[1]	(285)	[2]
Policyholder contract deposits	0		0
Policyholder contract withdrawals	0		0
Net cash flows (used for) from financing activities	(280)		(1,535)
Effect of foreign currency rate changes on cash and restricted cash	0		0
Net Increase (Decrease) in cash and restricted cash	(370)		(285)
Cash and Restricted Cash - Beginning of year	(652)		(115)
Cash and Restricted Cash - end of Year	$ (1,022)		$ (400)

[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, 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 March 31, 2018 and December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.