Schedule II (STATEMENTS OF CASH FLOWS - Parent Company Only) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2020		Dec. 31, 2019		Dec. 31, 2018
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		$ 9,785		$ 6,342		$ 5,480
Payment Of Contributions To Subsidiary		0		0		0
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(1,530)		(1,044)
Net proceeds from (payments to) affiliated notional cash pooling programs		0		0	[1]	0
Net cash flows (used for) from financing activities		(2,082)		(151)		(1,991)
Effect of foreign currency rate changes on cash and restricted cash		8		20		(65)
Cash and restricted cash – beginning of year		1,537	[2]	1,247
Cash and restricted cash – end of year		1,747	[3]	1,537	[2]	1,247
Payments for (Proceeds from) Other Investing Activities		470		657		533
Chubb limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Net cash flows from operating activities		1,933		412		256
Payment Of Contributions To Subsidiary		(1,200)		(1,000)		(1,475)
Net cash flows used for investing activities		(1,202)		(1,000)		(1,475)
Dividends paid on Common Shares		(1,388)		(1,354)		(1,337)
Common Shares repurchased		(523)		(327)		0
Payments To From Affiliates		1,265		2,301		2,519
Net proceeds from (payments to) affiliated notional cash pooling programs	[4]	0		(35)		35
Net cash flows (used for) from financing activities		(646)		585		1,217
Effect of foreign currency rate changes on cash and restricted cash		(3)		4		0
Net increase (decrease) in cash and restricted cash		82		1		(2)
Cash and restricted cash – beginning of year		2	[2]	1		3
Cash and restricted cash – end of year		84	[3]	2	[2]	1
Cash dividend paid by Affiliates	[5]	2,000		200		75
Payments for (Proceeds from) Other Investing Activities		$ (2)		$ 0		$ 0

[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, 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. Refer to Note 1 f) for additional information.

[3] 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.

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

[5] Includes cash dividends received from subsidiaries of $2.0 billion, $200 million, and $75 million in 2020, 2019, and 2018, respectively.