Information Provided In Connection With Outstanding Debt Of Subsidiaries (Condensed Consolidating Balance Sheet) (Detail) - USD ($) $ in Millions		Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		$ 118,979	$ 118,669
Cash		1,684	1,747
Total assets		191,977	190,774
Long-term debt		14,879	14,948
Trust preferred securities		308	308
Total liabilities		132,901	131,333
Total shareholders' equity		59,076	59,441	$ 52,197
Total liabilities and shareholders’ equity		191,977	190,774
Chubb Limited (Parent Guarantor)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments	[1]	0	0
Cash	[1]	23	84
Due from subsidiaries and affiliates, net	[1]	3,510	3,522
Other assets	[1]	8	10
Total assets	[1]	3,541	3,616
Due to subsidiaries and affiliates, net	[1]	0	0
Affiliated notional cash pooling programs	[1]	0	0
Long-term debt	[1]	0	0
Trust preferred securities	[1]	0	0
Other liabilities	[1]	337	323
Total liabilities	[1]	337	323
Total shareholders' equity	[1],[2]	3,204	3,293
Total liabilities and shareholders’ equity	[1]	3,541	3,616
Investments in subsidiaries		55,900	56,100
Chubb INA Holdings Inc (Subsidiary Issuer)
Condensed Balance Sheet Statements, Captions [Line Items]
Investments		206	197
Cash		1	1
Due from subsidiaries and affiliates, net		0	0
Other assets		415	463
Total assets		622	661
Due to subsidiaries and affiliates, net		3,079	3,008
Affiliated notional cash pooling programs		361	272
Long-term debt		14,879	14,948
Trust preferred securities		308	308
Other liabilities		1,281	1,418
Total liabilities		19,908	19,954
Total shareholders' equity	[2]	(19,286)	(19,293)
Total liabilities and shareholders’ equity		622	661
Investments in subsidiaries		$ 54,500	$ 55,200

[1] Excludes investment in subsidiary issuer (presented separately).

[2] Total shareholders' equity of Parent Guarantor excludes $55.9 billion and $56.1 billion of investment in subsidiaries, including Subsidiary Issuer, at March 31, 2021 and December 31, 2020, respectively. Total shareholders' equity of Subsidiary Issuer excludes $54.5 billion and $55.2 billion of investment in subsidiaries at March 31, 2021 and December 31, 2020, respectively.