Investments (Net Unrealized Gains Losses on Investments by Asset Class) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Net unrealized gains (losses) on investments	$ 37,113		$ 20,604		$ 24,957
Net unrealized losses on held to maturity securities transferred from available-for-sale	6
Other Long-term Investments [Member]
Net unrealized gains (losses) on investments	(7)	[1]	4	[1]	14	[1]
Available-for-sale Securities [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	33,625		18,029		23,876
Available-for-sale Securities [Member] | Equity Securities [Member]
Net unrealized gains (losses) on investments	2,940		2,907		1,518
Securities Related to Other Than Temporary Impairments [Member] | Fixed Maturities [Member]
Net unrealized gains (losses) on investments	349		110		(194)
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
Net unrealized gains (losses) on investments	$ 206	[2]	$ (446)	[2]	$ (257)	[2]

[1] As of December 31, 2014, includes $6 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 strategic in nature and are included in “Other assets.”

[2] See Note 21 for more information on cash flow hedges.