Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Sep. 30, 2017		Dec. 31, 2016		Sep. 30, 2016		Dec. 31, 2015
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	$ 102,424		$ 99,094
Cash	1,088	[1],[2]	985	[1],[3]	$ 870	[4]	$ 1,775	[4]
Insurance and reinsurance balances receivable	9,551		8,970
Reinsurance recoverable on losses and loss expenses	14,799		13,577
Reinsurance recoverable on policy benefits	193		182
Value of business acquired	339		355
Goodwill and other intangible assets	22,265		22,095
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	16,919		14,528
Total assets	167,578		159,786
Unpaid losses and loss expenses	64,153		60,540		61,347		37,303
Unearned premiums	15,456		14,779
Future policy benefits	5,307		5,036
Due to subsidiaries and affiliates, net	0		0
Affiliated notional cash pooling programs	0		0
Repurchase agreements	1,408		1,403
Short-term debt	1,020		500
Long-term debt	11,559		12,610
Trust preferred securities	308		308
Other liabilities	17,896		16,335
Total liabilities	117,107		111,511
Total shareholders' equity	50,471		48,275		48,372
Total liabilities and shareholders’ equity	167,578		159,786
Chubb Limited (Parent Guarantor)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	0		27
Cash	1	[1],[2]	1	[1],[3]	6	[4]	1	[4]
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	40,936		38,408
Due from subsidiaries and affiliates, net	9,913		10,482
Other assets	61		3
Total assets	50,911		48,921
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	85	[2]	363	[3]
Repurchase agreements	0		0
Short-term debt	0		0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	355		283
Total liabilities	440		646
Total shareholders' equity	50,471		48,275
Total liabilities and shareholders’ equity	50,911		48,921
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	169		485
Cash	0	[1],[2]	1	[1],[3]	2	[4]	2	[4]
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	50,926		49,509
Due from subsidiaries and affiliates, net	0		0
Other assets	276		436
Total assets	51,371		50,431
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	9,697		10,209
Affiliated notional cash pooling programs	2	[2]	619	[3]
Repurchase agreements	0		0
Short-term debt	1,020		500
Long-term debt	11,548		12,599
Trust preferred securities	308		308
Other liabilities	1,685		1,582
Total liabilities	24,260		25,817
Total shareholders' equity	27,111		24,614
Total liabilities and shareholders’ equity	51,371		50,431
Other Chubb Limited Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	102,255		98,582
Cash	1,174	[1],[2]	1,965	[1],[3]	2,158	[4]	2,743	[4]
Insurance and reinsurance balances receivable	11,076		10,498
Reinsurance recoverable on losses and loss expenses	27,007		24,496
Reinsurance recoverable on policy benefits	1,232		1,153
Value of business acquired	339		355
Goodwill and other intangible assets	22,265		22,095
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	20,699		18,442
Total assets	186,047		177,586
Unpaid losses and loss expenses	75,688		70,683
Unearned premiums	19,150		18,538
Future policy benefits	6,346		6,007
Due to subsidiaries and affiliates, net	216		273
Affiliated notional cash pooling programs	0	[2]	0	[3]
Repurchase agreements	1,408		1,403
Short-term debt	0		0
Long-term debt	11		11
Trust preferred securities	0		0
Other liabilities	18,477		17,368
Total liabilities	121,296		114,283
Total shareholders' equity	64,751		63,303
Total liabilities and shareholders’ equity	186,047		177,586
Consolidating Adjustments and Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	0		0
Cash	(87)	[1],[2]	(982)	[1],[3]	$ (1,296)	[4]	$ (971)	[4]
Insurance and reinsurance balances receivable	(1,525)		(1,528)
Reinsurance recoverable on losses and loss expenses	(12,208)		(10,919)
Reinsurance recoverable on policy benefits	(1,039)		(971)
Value of business acquired	0		0
Goodwill and other intangible assets	0		0
Investments in subsidiaries	(91,862)		(87,917)
Due from subsidiaries and affiliates, net	(9,913)		(10,482)
Other assets	(4,117)		(4,353)
Total assets	(120,751)		(117,152)
Unpaid losses and loss expenses	(11,535)		(10,143)
Unearned premiums	(3,694)		(3,759)
Future policy benefits	(1,039)		(971)
Due to subsidiaries and affiliates, net	(9,913)		(10,482)
Affiliated notional cash pooling programs	(87)	[2]	(982)	[3]
Repurchase agreements	0		0
Short-term debt	0		0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(2,621)		(2,898)
Total liabilities	(28,889)		(29,235)
Total shareholders' equity	(91,862)		(87,917)
Total liabilities and shareholders’ equity	$ (120,751)		$ (117,152)

[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, 2017 and December 31, 2016, 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, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] 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, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] 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, 2016 and December 31, 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.