Invested Assets (Details 1) (USD $) In Millions, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Fair value and amortized cost of fixed maturities by contractual maturity [Abstract]
Due in one year or less, Fair value	$ 2,353
Due after one year through five years, Fair value	12,565
Due after five years through ten years, Fair value	12,380
Due after ten years, Fair value	7,782
Subtotal fixed maturities, Fair value	35,080
Total fixed maturities, Fair Value	37,513	37,184
Due in one year or less, Amortized cost	2,326
Due after one year through five years, Amortized cost	11,919
Due after five years through ten years, Amortized cost	11,210
Due after ten years, Amortized cost	7,197
Subtotal fixed maturities, Amortized cost	32,652
Total fixed maturities, Amortized Cost	34,975	34,762
Residential mortgage-backed securities [Member]
Fair value and amortized cost of fixed maturities by contractual maturity [Abstract]
Taxable, Fair value	610
Taxable, Amortized cost	579
Commercial mortgage-backed securities [Member]
Fair value and amortized cost of fixed maturities by contractual maturity [Abstract]
Taxable, Fair value	1,823
Taxable, Amortized cost	$ 1,744