Claim and Claim Adjustment Expense Reserves - Changes in Provision for Insured Events of Prior Years (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Decrease in provision for insured events of prior years	$ (36)	$ (115)	$ (182)
Property and Casualty Reserve Development [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Decrease in provision for insured events of prior years	(39)	(115)	(180)
Life Reserve Development in Life Company [Member]
Causes of Increase (Decrease) in Liability for Unpaid Claims and Claims Adjustment Expense [Line Items]
Decrease in provision for insured events of prior years	$ 3		$ (2)