Reinsurance - Earned Consolidated Property Casualty Insurance Premiums on Assumed and Ceded Business (Detail) (Consolidated Property and Casualty Insurance Entity, USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Consolidated Property and Casualty Insurance Entity
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 1,067	$ 1,002	$ 3,134	$ 2,895
Assumed earned premiums	3	3	8	8
Ceded earned premiums	(45)	(51)	(132)	(150)
Net earned premiums	$ 1,025	$ 954	$ 3,010	$ 2,753