Schedule II (STATEMENTS OF CASH FLOWS - Parent Company Only) (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2015
Condensed Financial Statements, Captions [Line Items]
Purchases of fixed maturities available for sale		$ (25,720)		$ (30,759)		$ (16,040)
Sales of fixed maturities available for sale		13,228		16,621		10,783
Net change in short-term investments		(537)		12,350		(8,216)
Net derivative instruments settlements		(265)		(168)		(21)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		(2,442)		(5,315)		(6,294)
Other		114		(10)		263
Dividends paid on Common Shares		(1,308)		(1,173)		(862)
Proceeds from issuance of repurchase agreements		2,353		2,310		2,029
Repayments of Short-term Debt		2,348		2,311		2,027
Proceeds from share-based compensation plans		151		167		131
Net increase (decrease) in cash		(257)		(790)		1,120
Cash – beginning of year		985	[1],[2],[3]	1,775	[2],[4]	655	[4]
Cash – end of year	[2]	728	[5]	985	[1],[3]	1,775	[4]
Chubb limited (Parent Guarantor)
Condensed Financial Statements, Captions [Line Items]
Payments To From Affiliates		892		404		(228)
Cash dividend paid by Affiliates		450		3,400		2,900
Net cash flows from operating activities		781		3,618		3,125
Net change in short-term investments		0		0		0
Net derivative instruments settlements		0		0		0
Capital contributions to subsidiaries		0		(2,330)		(2,670)
Net Cash Provided by (Used in) Investing Activities, Continuing Operations		0		(2,330)		(2,670)
Other						0
Dividends paid on Common Shares		(1,308)		(1,173)		(862)
Repayments of Short-term Debt		0				0
Net proceeds from (payments to) affiliated notional cash pooling programs		(363)		(519)		636
Proceeds from share-based compensation plans		0		0		0
Net cash flows (used for) from financing activities		(779)		(1,288)		(454)
Net increase (decrease) in cash		2		0		1
Cash – beginning of year		1	[1],[2],[3]	1	[2],[4]	0	[4]
Cash – end of year	[2]	$ 3	[5]	$ 1	[1],[3]	$ 1	[4]

[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, 2016 and 2015, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[2] 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, 2017 and 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[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, 2016, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[4] 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, 2015 and 2014, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.

[5] Chubb maintains two notional multicurrency cash pools (Pools) with a third-party bank. Refer to Note 1 f) for additional information. At December 31, 2017, the cash balance of one or more entities was negative; however, the overall Pool balances were positive.