Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2019		Dec. 31, 2018		Sep. 30, 2018	Dec. 31, 2017
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	$ 107,178		$ 100,968
Cash	1,478	[1]	1,247	[2]
Restricted cash	111		93
Insurance and reinsurance balances receivable	10,403		10,075
Reinsurance recoverable on losses and loss expenses	15,527		15,993
Reinsurance recoverable on policy benefits	199		202
Operating Lease, Right-of-Use Asset	577
Value of business acquired	274		295
Goodwill and other intangible assets	21,378		21,414
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	18,600		17,484
Total assets	175,148		167,771
Unpaid losses and loss expenses	63,012		62,960		$ 63,029	$ 63,179
Unearned premiums	16,571		15,532
Future policy benefits	5,738		5,506
Due to subsidiaries and affiliates, net	0		0
Affiliated notional cash pooling programs	0	[1]	0	[2]
Operating Lease, Liability	617
Repurchase agreements	1,416		1,418
Short-term debt	10		509
Long-term debt	13,285		12,087
Trust preferred securities	308		308
Other liabilities	20,236		19,139
Total liabilities	120,576		117,459
Total shareholders' equity	54,572		50,312		$ 50,934
Total liabilities and shareholders’ equity	175,148		167,771
Chubb Limited (Parent Guarantor)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	0		0
Cash	2	[1]	1	[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	49,471		43,531
Due from subsidiaries and affiliates, net	6,068		7,074
Other assets	7		3
Total assets	55,548		50,609
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	628	[1]	35	[2]
Repurchase agreements	0		0
Short-term debt	0		0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	348		262
Total liabilities	976		297
Total shareholders' equity	54,572		50,312
Total liabilities and shareholders’ equity	55,548		50,609
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	227		214
Cash	0	[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	53,381		50,209
Due from subsidiaries and affiliates, net	0		0
Other assets	486		1,007
Total assets	54,094		51,432
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	5,953		7,672
Affiliated notional cash pooling programs	602	[1]	617	[2]
Repurchase agreements	0		0
Short-term debt	0		500
Long-term debt	13,285		12,086
Trust preferred securities	308		308
Other liabilities	1,814		2,545
Total liabilities	21,962		23,728
Total shareholders' equity	32,132		27,704
Total liabilities and shareholders’ equity	54,094		51,432
Other Chubb Limited Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	106,951		100,754
Cash	2,706	[1]	1,896	[2]
Restricted cash	111		93
Insurance and reinsurance balances receivable	12,519		11,861
Reinsurance recoverable on losses and loss expenses	25,284		26,422
Reinsurance recoverable on policy benefits	293		306
Value of business acquired	274		295
Goodwill and other intangible assets	21,378		21,414
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		598
Other assets	20,011		18,102
Total assets	189,527		181,741
Unpaid losses and loss expenses	72,389		72,857
Unearned premiums	17,767		16,611
Future policy benefits	5,832		5,610
Due to subsidiaries and affiliates, net	115		0
Affiliated notional cash pooling programs	0	[1]	0	[2]
Repurchase agreements	1,416		1,418
Short-term debt	10		9
Long-term debt	0		1
Trust preferred securities	0		0
Other liabilities	21,278		19,199
Total liabilities	118,807		115,705
Total shareholders' equity	70,720		66,036
Total liabilities and shareholders’ equity	189,527		181,741
Consolidating Adjustments and Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	0		0
Cash	(1,230)	[1]	(652)	[2]
Restricted cash	0		0
Insurance and reinsurance balances receivable	(2,116)		(1,786)
Reinsurance recoverable on losses and loss expenses	(9,757)		(10,429)
Reinsurance recoverable on policy benefits	(94)		(104)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(102,852)		(93,740)
Due from subsidiaries and affiliates, net	(6,068)		(7,672)
Other assets	(1,904)		(1,628)
Total assets	(124,021)		(116,011)
Unpaid losses and loss expenses	(9,377)		(9,897)
Unearned premiums	(1,196)		(1,079)
Future policy benefits	(94)		(104)
Due to subsidiaries and affiliates, net	(6,068)		(7,672)
Affiliated notional cash pooling programs	(1,230)	[1]	(652)	[2]
Repurchase agreements	0		0
Short-term debt	0		0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(3,204)		(2,867)
Total liabilities	(21,169)		(22,271)
Total shareholders' equity	(102,852)		(93,740)
Total liabilities and shareholders’ equity	$ (124,021)		$ (116,011)

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