Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012		Dec. 31, 2011
Net unrealized gains (losses) on investments	$ 24,076		$ 14,745
Net unrealized losses on held to maturity securities transferred from available-for-sale	80
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	(26)	[1]	(6)	[1]
Available-for-sale Securities [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	23,349		15,227
Available-for-sale Securities [Member] | Equity Securities [Member]
Net unrealized gains (losses) on investments	1,321		613
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	(443)		(1,003)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ (125)	[2]	$ (86)	[2]

[1] As of September 30, 2012, includes $80 million of net unrealized losses on held-to-maturity securities that were previously transferred from available-for-sale. Also includes net unrealized gains on certain joint ventures that are included in “Other assets.”

[2] See Note 14 for more information on cash flow hedges.