Investments (Held To Maturity Securities Continuous Unrealized Loss Position) (Detail) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Variable Interest Entity [Line Items]
Less than 12 Months, Fair Value		$ 284
Less than 12 Months, Unrealized Losses		(31)
12 Months or Longer, Fair Value	2,361	2,185
12 Months or Longer, Unrealized Losses	(160)	(340)
Total, Fair Value	2,361	2,469
Total, Unrealized Loss	(160)	(371)
Variable Interest Entity [Member] | Mortgage And Other Asset-Backed Securities [Member]
Variable Interest Entity [Line Items]
Less than 12 Months, Fair Value		284
Less than 12 Months, Unrealized Losses		(31)
12 Months or Longer, Fair Value	2,361	2,185
12 Months or Longer, Unrealized Losses	(160)	(340)
Total, Fair Value	2,361	2,469
Total, Unrealized Loss	$ (160)	$ (371)