Fair Value Measurements (Details 4) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010	Dec. 31, 2009
Financial assets:
Cash and cash equivalents	$ 1,705		$ 1,324		$ 1,099	$ 1,120
Mortgage loans	607		401
Policy loans	228		252
Financial liabilities:
Long-term debt	953		934
Level 1 [Member]
Financial assets:
Cash and cash equivalents	1,705		1,324
Total financial assets not accounted for at fair value	1,705		1,324
Level 2 [Member]
Financial liabilities:
Long-term debt	990		891
Total financial liabilities not accounted for at fair value	990		891
Level 3 [Member]
Financial assets:
Mortgage loans	613		401
Policy loans	228		252
Total financial assets not accounted for at fair value	841		653
Financial liabilities:
Annuity benefits accumulated	17,422	[1]	15,314	[1]
Long-term debt	96		119
Total financial liabilities not accounted for at fair value	17,518		15,433
Carrying Value [Member]
Financial assets:
Cash and cash equivalents	1,705		1,324
Mortgage loans	607		401
Policy loans	228		252
Total financial assets not accounted for at fair value	2,540		1,977
Financial liabilities:
Annuity benefits accumulated	17,405	[1]	15,219	[1]
Long-term debt	953		934
Total financial liabilities not accounted for at fair value	18,358		16,153
Fair Value [Member]
Financial assets:
Cash and cash equivalents	1,705		1,324
Mortgage loans	613		401
Policy loans	228		252
Total financial assets not accounted for at fair value	2,546		1,977
Financial liabilities:
Annuity benefits accumulated	17,422	[1]	15,314	[1]
Long-term debt	1,086		1,010
Total financial liabilities not accounted for at fair value	$ 18,508		$ 16,324

[1] Excludes life contingent annuities in the payout phase.