Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Net unrealized gains (losses) on investments	$ 20,067		$ 14,745
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	33	[1]	(6)
Available-for-sale Securities [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	19,763		15,227
Available-for-sale Securities [Member] | Equity Securities [Member]
Net unrealized gains (losses) on investments	1,049		613
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	(769)		(1,003)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ (9)	[2]	$ (86)	[2]

[1] As of June 30, 2012, includes $79 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.