Schedule IV (Reinsurance) (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Direct Amount	$ 17	$ (5)	$ (19)
Ceded to Others	2	3	(229)
Assumed From Other Companies	2	(2)	7
Net Amount	$ 17	$ (10)	$ 217
Percentage of Amount Assumed to Net	12.00%	20.00%	3.00%