Invested Assets and Related Income (Details 2) (Foreign government and government agency obligations [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Canada [Member]
Fair value and amortized cost for the foreign government and government agency fixed maturities for each country in which the Corporation's aggregate investment was 5% or more total foreign government and government agency fixed maturities [Abstract]
Fair value	$ 2,075
Amortized cost	1,943
United Kingdom [Member]
Fair value and amortized cost for the foreign government and government agency fixed maturities for each country in which the Corporation's aggregate investment was 5% or more total foreign government and government agency fixed maturities [Abstract]
Fair value	1,275
Amortized cost	1,145
Germany [Member]
Fair value and amortized cost for the foreign government and government agency fixed maturities for each country in which the Corporation's aggregate investment was 5% or more total foreign government and government agency fixed maturities [Abstract]
Fair value	897
Amortized cost	855
Australia [Member]
Fair value and amortized cost for the foreign government and government agency fixed maturities for each country in which the Corporation's aggregate investment was 5% or more total foreign government and government agency fixed maturities [Abstract]
Fair value	623
Amortized cost	$ 579