Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions		Mar. 31, 2018		Dec. 31, 2017		Mar. 31, 2017	Dec. 31, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		$ 102,105		$ 102,444
Cash		1,988	[1]	728	[2]
Restricted Cash	[1]	125		123
Insurance and reinsurance balances receivable		9,570		9,334
Reinsurance Recoverable Losses And Loss Expenses		14,982		15,034
Reinsurance recoverable on policy benefits		181		184
Value of business acquired		321		326
Goodwill and other intangible assets		22,123		22,054
Investments in subsidiaries		0		0
Due from subsidiaries and affiliates, net		0		0
Other assets		17,386		16,795
Total assets		168,781		167,022
Unpaid losses and loss expenses		63,139		63,179		$ 60,579	$ 60,540
Unearned premiums		15,495		15,216
Future policy benefits		5,412		5,321
Due to subsidiaries and affiliates, net		0		0
Affiliated notional cash pooling programs		0		0
Repurchase agreements		1,412		1,408
Short-term debt		1,669		1,013
Long-term debt		12,786		11,556
Trust preferred securities		308		308
Other liabilities		17,273		17,849
Total liabilities		117,494		115,850
Total shareholders' equity		51,287		51,172		$ 49,224
Total liabilities and shareholders’ equity		168,781		167,022
Chubb Limited (Parent Guarantor)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		0		0
Cash		1	[1]	3	[2]
Restricted Cash	[1]	0		0
Insurance and reinsurance balances receivable		0		0
Reinsurance Recoverable 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		43,032		41,909
Due from subsidiaries and affiliates, net		8,980		9,639
Other assets		4		3
Total assets		52,017		51,554
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		400	[1]	0	[2]
Repurchase agreements		0		0
Short-term debt		0		0
Long-term debt		0		0
Trust preferred securities		0		0
Other liabilities		330		382
Total liabilities		730		382
Total shareholders' equity		51,287		51,172
Total liabilities and shareholders’ equity		52,017		51,554
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		186		168
Cash		864	[1]	1	[2]
Restricted Cash	[1]	0		0
Insurance and reinsurance balances receivable		0		0
Reinsurance Recoverable 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		51,930		51,165
Due from subsidiaries and affiliates, net		0		0
Other assets		386		287
Total assets		53,366		51,621
Unpaid losses and loss expenses		0		0
Unearned premiums		0		0
Future policy benefits		0		0
Due to subsidiaries and affiliates, net		9,231		9,432
Affiliated notional cash pooling programs		0	[1]	115	[2]
Repurchase agreements		0		0
Short-term debt		1,669		1,013
Long-term debt		12,775		11,546
Trust preferred securities		308		308
Other liabilities		1,537		1,411
Total liabilities		25,520		23,825
Total shareholders' equity		27,846		27,796
Total liabilities and shareholders’ equity		53,366		51,621
Other Chubb Limited Subsidiaries
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		101,919		102,276
Cash		1,523	[1]	839	[2]
Restricted Cash	[1]	125		123
Insurance and reinsurance balances receivable		10,308		10,820
Reinsurance Recoverable Losses And Loss Expenses		26,093		27,514
Reinsurance recoverable on policy benefits		1,181		1,194
Value of business acquired		321		326
Goodwill and other intangible assets		22,123		22,054
Investments in subsidiaries		0		0
Due from subsidiaries and affiliates, net		251		0
Other assets		18,459		20,578
Total assets		182,303		185,724
Unpaid losses and loss expenses		74,299		74,767
Unearned premiums		16,563		18,875
Future policy benefits		6,412		6,331
Due to subsidiaries and affiliates, net		0		207
Affiliated notional cash pooling programs		0	[1]	0	[2]
Repurchase agreements		1,412		1,408
Short-term debt		0		0
Long-term debt		11		10
Trust preferred securities		0		0
Other liabilities		16,490		18,848
Total liabilities		115,187		120,446
Total shareholders' equity		67,116		65,278
Total liabilities and shareholders’ equity		182,303		185,724
Consolidating Adjustments and Eliminations
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		0		0
Cash		(400)	[1]	(115)	[2]
Restricted Cash	[1]	0		0
Insurance and reinsurance balances receivable		(738)		(1,486)
Reinsurance Recoverable Losses And Loss Expenses		(11,111)		(12,480)
Reinsurance recoverable on policy benefits		(1,000)		(1,010)
Value of business acquired		0		0
Goodwill and other intangible assets		0		0
Investments in subsidiaries		(94,962)		(93,074)
Due from subsidiaries and affiliates, net		(9,231)		(9,639)
Other assets		(1,463)		(4,073)
Total assets		(118,905)		(121,877)
Unpaid losses and loss expenses		(11,160)		(11,588)
Unearned premiums		(1,068)		(3,659)
Future policy benefits		(1,000)		(1,010)
Due to subsidiaries and affiliates, net		(9,231)		(9,639)
Affiliated notional cash pooling programs		(400)	[1]	(115)	[2]
Repurchase agreements		0		0
Short-term debt		0		0
Long-term debt		0		0
Trust preferred securities		0		0
Other liabilities		(1,084)		(2,792)
Total liabilities		(23,943)		(28,803)
Total shareholders' equity		(94,962)		(93,074)
Total liabilities and shareholders’ equity		$ (118,905)		$ (121,877)

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