Fair Value Measurements (Details 4) (USD $) In Millions, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012		Jun. 30, 2012	Dec. 31, 2011
Financial assets:
Cash and cash equivalents	$ 1,271		$ 1,705		$ 1,523	$ 1,324
Mortgage loans	599		607
Policy loans	242		228
Financial liabilities:
Long-term debt	949		953
Level 1 [Member]
Financial assets:
Cash and cash equivalents	1,271		1,705
Total financial assets not accounted for at fair value	1,271		1,705
Level 2 [Member]
Financial liabilities:
Long-term debt	975		990
Total financial liabilities not accounted for at fair value	975		990
Level 3 [Member]
Financial assets:
Mortgage loans	603		613
Policy loans	242		228
Total financial assets not accounted for at fair value	845		841
Financial liabilities:
Annuity benefits accumulated	17,865	[1]	17,422	[1]
Long-term debt	92		96
Total financial liabilities not accounted for at fair value	17,957		17,518
Carrying Value [Member]
Financial assets:
Cash and cash equivalents	1,271		1,705
Mortgage loans	599		607
Policy loans	242		228
Total financial assets not accounted for at fair value	2,112		2,540
Financial liabilities:
Annuity benefits accumulated	18,648	[1]	17,405	[1]
Long-term debt	949		953
Total financial liabilities not accounted for at fair value	19,597		18,358
Fair Value [Member]
Financial assets:
Cash and cash equivalents	1,271		1,705
Mortgage loans	603		613
Policy loans	242		228
Total financial assets not accounted for at fair value	2,116		2,546
Financial liabilities:
Annuity benefits accumulated	17,865	[1]	17,422	[1]
Long-term debt	1,067		1,086
Total financial liabilities not accounted for at fair value	$ 18,932		$ 18,508

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