Investments (Average Credit Ratings For Securities Rated Below Investment Grade Without The Effect Of Financial Guarantees) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013
Asset-backed [Member]
Schedule Of Investments [Line Items]
Fair Value Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	$ 105
Percentage Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	65.00%
Mortgage-backed [Member]
Schedule Of Investments [Line Items]
Fair Value Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	15
Percentage Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	87.00%
Corporate Obligations [Member]
Schedule Of Investments [Line Items]
Fair Value Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	$ 0
Percentage Of Securities Rated Below Investment Grade Without Giving Effect To Benefit Of Guarantees Provided By Financial Guarantors	0.00%