Loss And Loss Adjustment Expense Reserves (RMBS Recoveries) (Narrative) (Detail) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Loss And Loss Adjustment Expense Reserves [Line Items]
Remaining weighted average contract period (in years)	9 years 0 months 0 days	9 years 8 months 12 days
Second-Lien RMBS Ineligible Mortgage Loans [Member]
Loss And Loss Adjustment Expense Reserves [Line Items]
Contract claims on ineligible mortgage loans inception to date, incurred loss on transactions	$ 432