Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions		1 Months Ended	12 Months Ended
		Jan. 31, 2020	Dec. 31, 2019		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments			$ 109,234		$ 100,968
Cash			1,537	[1]	1,247	[2]	$ 728
Restricted Cash			109		93		123
Insurance and reinsurance balances receivable			10,357		10,075
Reinsurance recoverable on losses and loss expenses			15,181		15,993
Reinsurance Recoverable Future Policy Benefits			197		202
Value of business acquired			306		295		326	$ 355
Goodwill			21,359		21,414
Investments in subsidiaries			0		0
Due from subsidiaries and affiliates, net			0		0
Other assets			18,663		17,484
Total assets			176,943		167,771
Unpaid losses and loss expenses			62,690		62,960		63,179	60,540
Unearned premiums			16,771		15,532
Future policy benefits			5,814		5,506
Due to subsidiaries and affiliates, net			0		0
Affiliated notional cash pooling program	[2]				0
Repurchase agreements			1,416		1,418
Short-term debt			1,299		509
Long-term debt			13,559		12,087
Trust preferred securities			308		308
Other liabilities			19,755		19,139
Total liabilities			121,612		117,459
Total shareholders' equity			55,331		50,312
Total liabilities and shareholders’ equity			176,943		167,771
Advances To From Affiliates Financing Activities			0		0		0
Payment Of Contributions To Subsidiary			0		0
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments			0		0
Cash	[2]				(652)
Restricted Cash			0		0
Insurance and reinsurance balances receivable			(2,563)		(1,786)
Reinsurance recoverable on losses and loss expenses			(9,599)		(10,429)
Reinsurance Recoverable Future Policy Benefits			(95)		(104)
Value of business acquired			0		0
Goodwill			0		0
Investments in subsidiaries			(102,929)		(93,740)
Due from subsidiaries and affiliates, net			(4,776)		(7,672)
Other assets			(1,829)		(1,628)
Total assets			(121,791)		(116,011)
Unpaid losses and loss expenses			(9,226)		(9,897)
Unearned premiums			(1,207)		(1,079)
Future policy benefits			(95)		(104)
Due to subsidiaries and affiliates, net			(4,776)		(7,672)
Affiliated notional cash pooling program	[2]				(652)
Repurchase agreements			0		0
Short-term debt			0		0
Long-term debt			0		0
Trust preferred securities			0		0
Other liabilities			(3,558)		(2,867)
Total liabilities			(18,862)		(22,271)
Total shareholders' equity			(102,929)		(93,740)
Total liabilities and shareholders’ equity			(121,791)		(116,011)
Advances To From Affiliates Financing Activities			0		0		0
Payment Of Contributions To Subsidiary			1,110		5,025
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments			0		0
Cash			2	[1]	1	[2]	3	$ 1
Restricted Cash			0		0
Insurance and reinsurance balances receivable			0		0
Reinsurance recoverable on losses and loss expenses			0		0
Reinsurance Recoverable Future Policy Benefits			0		0
Value of business acquired			0		0
Goodwill			0		0
Investments in subsidiaries			50,853		43,531
Due from subsidiaries and affiliates, net			4,776		7,074
Other assets			12		3
Total assets			55,643		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 program	[3]		0		35	[2]
Repurchase agreements			0		0
Short-term debt			0		0
Long-term debt			0		0
Trust preferred securities			0		0
Other liabilities			312		262
Total liabilities			312		297
Total shareholders' equity			55,331		50,312
Total liabilities and shareholders’ equity			55,643		50,609
Advances To From Affiliates Financing Activities			(2,301)		(2,519)		(892)
Payment Of Contributions To Subsidiary			(1,000)		(1,475)
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments			1,013		214
Cash			442	[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 Future Policy Benefits			0		0
Value of business acquired			0		0
Goodwill			0		0
Investments in subsidiaries			52,076		50,209
Due from subsidiaries and affiliates, net			0		0
Other assets			408		1,007
Total assets			53,939		51,432
Unpaid losses and loss expenses			0		0
Unearned premiums			0		0
Future policy benefits			0		0
Due to subsidiaries and affiliates, net			4,446		7,672
Affiliated notional cash pooling program	[2]				617
Repurchase agreements			0		0
Short-term debt			1,298		500
Long-term debt			13,559		12,086
Trust preferred securities			308		308
Other liabilities			1,649		2,545
Total liabilities			21,260		23,728
Total shareholders' equity			32,679		27,704
Total liabilities and shareholders’ equity			53,939		51,432
Advances To From Affiliates Financing Activities			3,223		1,744		927
Payment Of Contributions To Subsidiary			(110)		(3,550)
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments			108,221		100,754
Cash			1,093	[1]	1,896	[2]
Restricted Cash			109		93
Insurance and reinsurance balances receivable			12,920		11,861
Reinsurance recoverable on losses and loss expenses			24,780		26,422
Reinsurance Recoverable Future Policy Benefits			292		306
Value of business acquired			306		295
Goodwill			21,359		21,414
Investments in subsidiaries			0		0
Due from subsidiaries and affiliates, net					598
Other assets			20,072		18,102
Total assets			189,152		181,741
Unpaid losses and loss expenses			71,916		72,857
Unearned premiums			17,978		16,611
Future policy benefits			5,909		5,610
Due to subsidiaries and affiliates, net			330
Affiliated notional cash pooling program	[2]				0
Repurchase agreements			1,416		1,418
Short-term debt			1		9
Long-term debt					1
Trust preferred securities			0		0
Other liabilities			21,352		19,199
Total liabilities			118,902		115,705
Total shareholders' equity			70,250		66,036
Total liabilities and shareholders’ equity			189,152		181,741
Advances To From Affiliates Financing Activities			$ (922)		$ 775		$ (35)
Subsequent Event [Member] | Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Payment Of Contributions To Subsidiary		$ 1,200
Subsequent Event [Member] | Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Advances To From Affiliates Financing Activities		$ (1,500)

[1] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.

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

[3] ⁽¹⁾ Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information.