Investments (Credit Ratings Of Asset-Backed And Mortgage-Backed Securities And Corporate Obligations In Available-For-Sale Investments For Which Fair Value Was Less Than Amortized Cost) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]
Fair value	$ 3,457	$ 1,284
Gross unrealized losses	(229)	(152)
Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	208
Gross unrealized losses	(72)
Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	907
Gross unrealized losses	(37)
Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	870
Gross unrealized losses	(38)
Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1,985
Gross unrealized losses	(147)
Moody's Aaa [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	16
Gross unrealized losses	0
Moody's Aaa [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	868
Gross unrealized losses	(31)
Moody's Aaa [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	151
Gross unrealized losses	(1)
Moody's Aaa [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1,035
Gross unrealized losses	(32)
Moodys Aa 1 Rating [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	62
Gross unrealized losses	(4)
Moodys Aa 1 Rating [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	7
Gross unrealized losses	0
Moodys Aa 1 Rating [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	238
Gross unrealized losses	(9)
Moodys Aa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	307
Gross unrealized losses	(13)
Moody's A1 [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1
Gross unrealized losses	0
Moody's A1 [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	4
Gross unrealized losses	0
Moody's A1 [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	275
Gross unrealized losses	(12)
Moody's A1 [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	280
Gross unrealized losses	(12)
Moody's Baa 1 Rating [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	2
Gross unrealized losses	0
Moody's Baa 1 Rating [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	6
Gross unrealized losses	(1)
Moody's Baa 1 Rating [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	76
Gross unrealized losses	(5)
Moody's Baa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	84
Gross unrealized losses	(6)
Below Investment Grade [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	126
Gross unrealized losses	(68)
Below Investment Grade [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	7
Gross unrealized losses	(1)
Below Investment Grade [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	17
Gross unrealized losses	(1)
Below Investment Grade [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	150
Gross unrealized losses	(70)
Not Rated [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1
Gross unrealized losses	0
Not Rated [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	15
Gross unrealized losses	(4)
Not Rated [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	113
Gross unrealized losses	(10)
Not Rated [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	129
Gross unrealized losses	$ (14)