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
	Mar. 31, 2015	Mar. 31, 2014
Consolidated Property and Casualty Insurance Entity
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 1,076	$ 1,019
Assumed earned premiums	2	3
Ceded earned premiums	(37)	(43)
Earned premiums	$ 1,041	$ 979