Reinsurance - Earned Consolidated Property Casualty Insurance Premiums on Assumed and Ceded Business (Detail) - Consolidated Property and Casualty Insurance Entity - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 1,110	$ 1,067	$ 3,279	$ 3,134
Assumed earned premiums	3	3	8	8
Ceded earned premiums	(37)	(45)	(111)	(132)
Earned premiums	$ 1,076	$ 1,025	$ 3,176	$ 3,010