Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions		Jun. 30, 2020		Dec. 31, 2019		Jun. 30, 2019	Dec. 31, 2018
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		$ 110,877		$ 109,234
Cash		1,557	[1]	1,537	[2]
Restricted cash		152		109
Insurance and reinsurance balances receivable		10,853		10,357
Reinsurance recoverable on losses and loss expenses		15,207		15,181
Reinsurance recoverable on policy benefits		197		197
Operating Lease, Right-of-Use Asset		483		551
Value of business acquired		290		306
Goodwill and other intangible assets		21,093		21,359
Investments in subsidiaries		0		0
Due from subsidiaries and affiliates, net		0		0
Other assets		21,248		18,663
Total assets		181,474		176,943
Unpaid losses and loss expenses		65,699		62,690		$ 63,205	$ 62,960
Unearned premiums		17,081		16,771
Future policy benefits		5,895		5,814
Due to subsidiaries and affiliates, net		0		0
Affiliated notional cash pooling programs		0
Operating Lease, Liability		531		603
Repurchase agreements		1,409		1,416
Short-term debt		1,300		1,299
Long-term debt		13,656		13,559
Trust preferred securities		308		308
Other liabilities		21,366		19,755
Total liabilities		126,714		121,612
Total shareholders' equity		54,760		55,331		$ 53,802
Total liabilities and shareholders’ equity		181,474		176,943
Chubb Limited (Parent Guarantor)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		0		0
Cash		1	[1]	2	[2]
Restricted cash		0		0
Insurance and reinsurance balances receivable		0		0
Reinsurance recoverable on losses and loss expenses		0		0
Reinsurance recoverable on policy benefits		0		0
Value of business acquired		0		0
Goodwill and other intangible assets		0		0
Investments in subsidiaries		52,339		50,853
Due from subsidiaries and affiliates, net		3,636		4,776
Other assets		8		12
Total assets		55,984		55,643
Unpaid losses and loss expenses		0		0
Unearned premiums		0		0
Future policy benefits		0		0
Due to subsidiaries and affiliates, net		0		0
Affiliated notional cash pooling programs	[1]	882
Repurchase agreements		0		0
Short-term debt		0		0
Long-term debt		0		0
Trust preferred securities		0		0
Other liabilities		342		312
Total liabilities		1,224		312
Total shareholders' equity		54,760		55,331
Total liabilities and shareholders’ equity		55,984		55,643
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		195		1,013
Cash		0	[1]	442	[2]
Restricted cash		0		0
Insurance and reinsurance balances receivable		0		0
Reinsurance recoverable on losses and loss expenses		0		0
Reinsurance recoverable on policy benefits		0		0
Value of business acquired		0		0
Goodwill and other intangible assets		0		0
Investments in subsidiaries		52,752		52,076
Due from subsidiaries and affiliates, net		0		0
Other assets		336		408
Total assets		53,283		53,939
Unpaid losses and loss expenses		0		0
Unearned premiums		0		0
Future policy benefits		0		0
Due to subsidiaries and affiliates, net		3,365		4,446
Affiliated notional cash pooling programs	[1]	186
Repurchase agreements		0		0
Short-term debt		1,300		1,298
Long-term debt		13,656		13,559
Trust preferred securities		308		308
Other liabilities		1,415		1,649
Total liabilities		20,230		21,260
Total shareholders' equity		33,053		32,679
Total liabilities and shareholders’ equity		53,283		53,939
Other Chubb Limited Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		110,682		108,221
Cash		2,624	[1]	1,093	[2]
Restricted cash		152		109
Insurance and reinsurance balances receivable		13,637		12,920
Reinsurance recoverable on losses and loss expenses		24,804		24,780
Reinsurance recoverable on policy benefits		292		292
Value of business acquired		290		306
Goodwill and other intangible assets		21,093		21,359
Investments in subsidiaries		0		0
Due from subsidiaries and affiliates, net		0		0
Other assets		22,858		20,072
Total assets		196,432		189,152
Unpaid losses and loss expenses		75,013		71,916
Unearned premiums		18,301		17,978
Future policy benefits		5,990		5,909
Due to subsidiaries and affiliates, net		271		330
Affiliated notional cash pooling programs	[1]	0
Repurchase agreements		1,409		1,416
Short-term debt		0		1
Long-term debt		0		0
Trust preferred securities		0		0
Other liabilities		23,410		21,352
Total liabilities		124,394		118,902
Total shareholders' equity		72,038		70,250
Total liabilities and shareholders’ equity		196,432		189,152
Consolidating Adjustments and Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		0		0
Cash		(1,068)	[1]	0	[2]
Restricted cash		0		0
Insurance and reinsurance balances receivable		(2,784)		(2,563)
Reinsurance recoverable on losses and loss expenses		(9,597)		(9,599)
Reinsurance recoverable on policy benefits		(95)		(95)
Value of business acquired		0		0
Goodwill and other intangible assets		0		0
Investments in subsidiaries		(105,091)		(102,929)
Due from subsidiaries and affiliates, net		(3,636)		(4,776)
Other assets		(1,954)		(1,829)
Total assets		(124,225)		(121,791)
Unpaid losses and loss expenses		(9,314)		(9,226)
Unearned premiums		(1,220)		(1,207)
Future policy benefits		(95)		(95)
Due to subsidiaries and affiliates, net		(3,636)		(4,776)
Affiliated notional cash pooling programs	[1]	(1,068)
Repurchase agreements		0		0
Short-term debt		0		0
Long-term debt		0		0
Trust preferred securities		0		0
Other liabilities		(3,801)		(3,558)
Total liabilities		(19,134)		(18,862)
Total shareholders' equity		(105,091)		(102,929)
Total liabilities and shareholders’ equity		$ (124,225)		$ (121,791)

[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, 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. Refer to the 2019 Form 10-K for additional information.