Information provided in connection with outstanding debt of subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions	Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	$ 118,669		$ 109,234
Cash	1,747	[1]	1,537	[2]	$ 1,247
Restricted Cash	89		109		93
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	10,480		10,357
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	15,592		15,181
Reinsurance Recoverable Future Policy Benefits	206		197
Value of business acquired	263		306		295	$ 326
Goodwill	21,211		21,359
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	0		0
Other assets	22,517		18,663
Total assets	190,774		176,943
Unpaid losses and loss expenses	67,811		62,690		62,960	63,179
Unearned premiums	17,652		16,771
Future policy benefits	5,713		5,373
Due to subsidiaries and affiliates, net	0		0
Affiliated notional cash pooling programs	0
Repurchase agreements	1,405		1,416
Short-term debt	0		1,299
Long-term debt	14,948		13,559
Trust preferred securities	308		308
Other liabilities	23,496		20,196
Total liabilities	131,333		121,612
Total shareholders' equity	59,441		55,331
Total liabilities and shareholders’ equity	190,774		176,943
Consolidating Adjustments
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	0		0
Cash	(272)	[1]	0	[2]
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	(3,446)		(2,563)
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	(9,625)		(9,599)
Reinsurance Recoverable Future Policy Benefits	(93)		(95)
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	(111,379)		(102,929)
Due from subsidiaries and affiliates, net	(3,693)		(4,776)
Other assets	(1,877)		(1,829)
Total assets	(130,385)		(121,791)
Unpaid losses and loss expenses	(9,369)		(9,226)
Unearned premiums	(1,201)		(1,207)
Future policy benefits	(93)		(95)
Due to subsidiaries and affiliates, net	(3,693)		(4,776)
Affiliated notional cash pooling programs	(272)
Repurchase agreements	0		0
Short-term debt			0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	(4,378)		(3,558)
Total liabilities	(19,006)		(18,862)
Total shareholders' equity	(111,379)		(102,929)
Total liabilities and shareholders’ equity	(130,385)		(121,791)
Chubb limited (Parent Guarantor)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	0		0
Cash	84	[1]	2	[2]	$ 1	$ 3
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	0		0
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	0		0
Reinsurance Recoverable Future Policy Benefits	0		0
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	56,148		50,853
Due from subsidiaries and affiliates, net	3,522		4,776
Other assets	10		12
Total assets	59,764		55,643
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	0
Repurchase agreements	0		0
Short-term debt			0
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	323		312
Total liabilities	323		312
Total shareholders' equity	59,441		55,331
Total liabilities and shareholders’ equity	59,764		55,643
Chubb INA Holdings Inc. (Subsidiary Issuer)
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	197		1,013
Cash	1	[1]	442	[2]
Restricted Cash	0		0
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	0		0
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	0		0
Reinsurance Recoverable Future Policy Benefits	0		0
Value of business acquired	0		0
Goodwill	0		0
Investments in subsidiaries	55,231		52,076
Due from subsidiaries and affiliates, net	0		0
Other assets	463		408
Total assets	55,892		53,939
Unpaid losses and loss expenses	0		0
Unearned premiums	0		0
Future policy benefits	0		0
Due to subsidiaries and affiliates, net	3,008		4,446
Affiliated notional cash pooling programs	272
Repurchase agreements	0		0
Short-term debt			1,298
Long-term debt	14,948		13,559
Trust preferred securities	308		308
Other liabilities	1,418		1,649
Total liabilities	19,954		21,260
Total shareholders' equity	35,938		32,679
Total liabilities and shareholders’ equity	55,892		53,939
Other Chubb Limited Subsidiaries and Eliminations
Information Provided In Connection With Outstanding Debt Of Subsidiaries [Line Items]
Investments	118,472		108,221
Cash	1,934	[1]	1,093	[2]
Restricted Cash	89		109
Insurance and reinsurance balances receivable, net of valuation allowance - $44 and $44	13,926		12,920
Reinsurance recoverable on losses and loss expenses, net of valuation allowance - $314 and $316	25,217		24,780
Reinsurance Recoverable Future Policy Benefits	299		292
Value of business acquired	263		306
Goodwill	21,211		21,359
Investments in subsidiaries	0		0
Due from subsidiaries and affiliates, net	171		0
Other assets	23,921		20,072
Total assets	205,503		189,152
Unpaid losses and loss expenses	77,180		71,916
Unearned premiums	18,853		17,978
Future policy benefits	5,806		5,468
Due to subsidiaries and affiliates, net	685		330
Affiliated notional cash pooling programs	0
Repurchase agreements	1,405		1,416
Short-term debt			1
Long-term debt	0		0
Trust preferred securities	0		0
Other liabilities	26,133		21,793
Total liabilities	130,062		118,902
Total shareholders' equity	75,441		70,250
Total liabilities and shareholders’ equity	$ 205,503		$ 189,152

[1] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2020, 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.