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		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 1,093	$ 1,048	$ 2,169	$ 2,067
Assumed earned premiums	3	2	5	5
Ceded earned premiums	(37)	(44)	(74)	(87)
Earned premiums	$ 1,059	$ 1,006	$ 2,100	$ 1,985