Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions		Dec. 31, 2017		Dec. 31, 2016		Jan. 14, 2016	Dec. 31, 2015		Dec. 31, 2014
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments		$ 102,444		$ 99,094
Cash		728	[1],[2]	985	[1],[3],[4]		$ 1,775	[1],[5]	$ 655	[5]
Insurance and reinsurance balances receivable		9,334		8,970
Reinsurance recoverable on losses and loss expenses		15,034		13,577
Reinsurance Recoverable Future Policy Benefits	[6]	184		182
Value of business acquired		326		355			395		466
Goodwill		22,054		22,095
Other assets		16,918		14,528
Total assets		167,022		159,786
Unpaid losses and loss expenses		63,179		60,540			37,303		38,315
Unearned premiums		15,216		14,779
Future policy benefits		5,321		5,036
Affiliated notional cash pooling program		300		0	[4]
Repurchase agreements		1,408		1,403
Short-term debt		1,013		500
Long-term debt		11,556		12,610
Trust preferred securities		308		308
Other liabilities		17,849		16,335
Total liabilities		115,850		111,511
Total shareholders' equity		51,172		48,275
Total liabilities and shareholders’ equity		167,022		159,786
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Cash		(115)	[1],[2]	(982)	[1],[3],[4]		(971)	[1],[5]	(555)	[5]
Insurance and reinsurance balances receivable		(1,486)		(1,528)
Reinsurance recoverable on losses and loss expenses		(12,480)		(10,919)
Reinsurance Recoverable Future Policy Benefits		(1,010)		(971)
Investments in subsidiaries		(93,074)		(87,917)
Due from subsidiaries and affiliates, net		(9,639)		(10,482)
Other assets		(4,073)		(4,353)
Total assets		(121,877)		(117,152)
Unpaid losses and loss expenses		(11,588)		(10,143)
Unearned premiums		(3,659)		(3,759)
Future policy benefits		(1,010)		(971)
Due to subsidiaries and affiliates, net		(9,639)		(10,482)
Affiliated notional cash pooling program		(115)	[2]	(982)	[4]
Repurchase agreements		0		0
Other liabilities		(2,792)		(2,898)
Total liabilities		(28,803)		(29,235)
Total shareholders' equity		(93,074)		(87,917)
Total liabilities and shareholders’ equity		(121,877)		(117,152)
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments				27
Cash		3	[1],[2]	1	[1],[3],[4]		1	[1],[5]	0	[5]
Investments in subsidiaries		41,909		38,408
Due from subsidiaries and affiliates, net		9,639		10,482
Other assets		3		3
Total assets		51,554		48,921
Affiliated notional cash pooling program		0		363	[4]
Repurchase agreements		0		0
Other liabilities		382		283
Total liabilities		382		646
Total shareholders' equity		51,172		48,275
Total liabilities and shareholders’ equity		51,554		48,921
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments		168		485
Cash		1	[1],[2]	1	[1],[3],[4]		2	[1],[5]	1	[5]
Investments in subsidiaries		51,165		49,509
Other assets		287		436
Total assets		51,621		50,431
Due to subsidiaries and affiliates, net		9,432		10,209
Affiliated notional cash pooling program		115	[2]	619	[4]
Repurchase agreements		0		0
Short-term debt		1,013		500
Long-term debt		11,546		12,599
Trust preferred securities		308		308
Other liabilities		1,411		1,582
Total liabilities		23,825		25,817
Total shareholders' equity		27,796		24,614
Total liabilities and shareholders’ equity		51,621		50,431
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments		102,276		98,582
Cash		839	[1],[2]	1,965	[1],[3],[4]		$ 2,743	[5]	$ 1,209	[5]
Insurance and reinsurance balances receivable		10,820		10,498
Reinsurance recoverable on losses and loss expenses		27,514		24,496
Reinsurance Recoverable Future Policy Benefits		1,194		1,153
Value of business acquired		326		355
Goodwill		22,054		22,095
Other assets		20,701		18,442
Total assets		185,724		177,586
Unpaid losses and loss expenses		74,767		70,683
Unearned premiums		18,875		18,538
Future policy benefits		6,331		6,007
Due to subsidiaries and affiliates, net		207		273
Repurchase agreements		1,408		1,403
Long-term debt		10		11
Other liabilities		18,848		17,368
Total liabilities		120,446		114,283
Total shareholders' equity		65,278		63,303
Total liabilities and shareholders’ equity		$ 185,724		$ 177,586
The Chubb Corporation [Member]
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments						$ 42,967
Cash						71
Insurance and reinsurance balances receivable						3,095
Unpaid losses and loss expenses						22,923
Unearned premiums						7,011
Long-term debt						$ 3,765

[1] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2017 and 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. Refer to Note 1 f) for additional information. At December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[3] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2016 and 2015, 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. Refer to Note 1 f) for additional information. At December 31, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[5] Chubb maintains two notional multi-currency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2015 and 2014, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[6] (1) Net of a provision for uncollectible reinsurance.