Accounting Policies (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Accounting Standards Adopted in 2012
Deferred policy acquisition costs	$ 550				$ 901				$ 550	$ 901	$ 1,031	$ 1,329
Net deferred tax liability (included in other liabilities)	251				133				251	133
Shareholders' equity	4,578				4,411				4,578	4,411
Net earnings attributable to shareholders	50	226	99	113	109	97	48	88	488	342	482
Diluted earnings per Common Share	$ 0.54	$ 2.39	$ 1.01	$ 1.14	$ 1.09	$ 0.95	$ 0.46	$ 0.83	$ 5.09	$ 3.32	$ 4.36
As previously reported [Member]
Accounting Standards Adopted in 2012
Deferred policy acquisition costs					1,105					1,105
Net deferred tax liability (included in other liabilities)					203					203
Shareholders' equity					4,545					4,545
Net earnings attributable to shareholders										343	479
Diluted earnings per Common Share										$ 3.33	$ 4.33
As adjusted [Member]
Accounting Standards Adopted in 2012
Deferred policy acquisition costs					901					901
Net deferred tax liability (included in other liabilities)					133					133
Shareholders' equity					4,411					4,411
Net earnings attributable to shareholders										$ 342	$ 482
Diluted earnings per Common Share										$ 3.32	$ 4.36