Insurance In Force (Summary Of Components Of Financial Guarantee Net Premiums Earned, Including Premiums Assumed From And Ceded To Other Companies) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Insurance in Force [Abstract]
Direct	$ 379	$ 407	$ 400
Assumed	2	2	67
Gross	381	409	467
Ceded premiums earned	(9)	(12)	(10)
Premiums earned (net of ceded premiums of $9, $12 and $10)	$ 372	$ 397	$ 457