Reinsurance - Earned Life Insurance Premiums on Ceded Business (Detail) (Life Insurance Segment, USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Life Insurance Segment
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Direct earned premiums	$ 56	$ 54
Assumed earned premiums	0	0
Ceded earned premiums	(14)	(13)
Net earned premiums	$ 42	$ 41