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	Jun. 30, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities [Line Items]
Fair value	$ 2,224	$ 3,457
Gross unrealized losses	(90)	(229)
Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	164
Gross unrealized losses	(32)
Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	496
Gross unrealized losses	(16)
Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	634
Gross unrealized losses	(21)
Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1,294
Gross unrealized losses	(69)
Moody's Aaa [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	27
Gross unrealized losses	0
Moody's Aaa [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	459
Gross unrealized losses	(12)
Moody's Aaa [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	68
Gross unrealized losses	0
Moody's Aaa [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	554
Gross unrealized losses	(12)
Moodys Aa 1 Rating [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	62
Gross unrealized losses	(3)
Moodys Aa 1 Rating [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	8
Gross unrealized losses	0
Moodys Aa 1 Rating [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	194
Gross unrealized losses	(3)
Moodys Aa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	264
Gross unrealized losses	(6)
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	2
Gross unrealized losses	0
Moody's A1 [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	220
Gross unrealized losses	(4)
Moody's A1 [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	223
Gross unrealized losses	(4)
Moody's Baa 1 Rating [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1
Gross unrealized losses	0
Moody's Baa 1 Rating [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	4
Gross unrealized losses	0
Moody's Baa 1 Rating [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	41
Gross unrealized losses	(2)
Moody's Baa 1 Rating [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	46
Gross unrealized losses	(2)
Below Investment Grade [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	73
Gross unrealized losses	(29)
Below Investment Grade [Member] | Mortgage-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	8
Gross unrealized losses	0
Below Investment Grade [Member] | Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	1
Gross unrealized losses	0
Below Investment Grade [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	82
Gross unrealized losses	(29)
Not Rated [Member] | Asset-backed [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	0
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	110
Gross unrealized losses	(12)
Not Rated [Member] | Total ABS MBS and Corporate Obligations [Member]
Schedule Of Available For Sale Securities [Line Items]
Fair value	125
Gross unrealized losses	$ (16)