General Schedule of Cash and Cash Equivalent (Details) - USD ($) $ in Millions		Sep. 30, 2018		Dec. 31, 2017		Sep. 30, 2017	Dec. 31, 2016
Cash and Cash Equivalents [Line Items]
Cash		$ 1,053	[1]	$ 728	[2]
Restricted Cash	[1]	104		123
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents		$ 1,157		851		$ 1,193	$ 1,088
Adjustments for New Accounting Pronouncement [Member]
Cash and Cash Equivalents [Line Items]
Restricted Cash				$ 123

[1] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At September 30, 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. Various Chubb entities participate in one or the other of the Pools, pursuant to which credit and debit balances in individual Chubb accounts are translated daily into a single currency and pooled on a notional basis. Individual Chubb entities are permitted to overdraw on their individual accounts provided the overall Pool balances do not fall below zero. At December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.