Reinsurance - Earned Consolidated Property Casualty Insurance Premiums on Assumed and Ceded Business (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Reinsurance Disclosures [Abstract]
Direct earned premiums	$ 1,048	$ 958	$ 2,067	$ 1,893
Assumed earned premiums	2	3	5	5
Ceded earned premiums	(44)	(51)	(87)	(99)
Net earned premiums	$ 1,006	$ 910	$ 1,985	$ 1,799