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, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 1,137	$ 1,093	$ 2,256	$ 2,169
Assumed earned premiums	16	3	31	5
Ceded earned premiums	(39)	(37)	(77)	(74)
Earned premiums	$ 1,114	$ 1,059	$ 2,210	$ 2,100