Reinsurance - Life Insurance Contract Holders' Benefits Incurred on Ceded Business (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Assumed earned premiums	$ 3	$ 1	$ 8	$ 7
Net incurred loss and loss expenses	642	571	1,841	1,840
Life Insurance Segment
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct policyholders' benefits incurred	64	62	190	172
Assumed policyholders' benefits incurred	0	0	0
Assumed earned premiums	0	0	0	0
Ceded policyholders' benefits incurred	(15)	(16)	(49)	(36)
Net incurred loss and loss expenses	$ 49	$ 46	$ 141	$ 136