Merger Agreement with ACE Limited - Additional Information (Detail)	Jun. 30, 2015 USD ($) $ / shares shares	Sep. 30, 2015 USD ($) $ / shares	Jun. 30, 2015 SFr / shares	Jun. 30, 2015 $ / shares	Dec. 31, 2014 $ / shares
Business Acquisition [Line Items]
Common Stock, Par Value		$ 1			$ 1
ACE Limited [Member]
Business Acquisition [Line Items]
Common Stock, Par Value				$ 1.00
Amount of common share of ACE converted from common stock of Chubb | shares	0.6019
ACE common stock, par value per share | SFr / shares			SFr 24.15
Cash received per share of Chubb common stock due to conversion to ACE common share	$ 62.93
Termination fee | $	$ 930,000,000
Accrued termination fee | $		$ 0