Deferred Policy Acquisition Costs and Present Value of Future Profits (Details Textual) (USD $) In Millions, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Dec. 31, 2011 Effect of change [Member]	Dec. 31, 2010 Effect of change [Member]	Dec. 31, 2011 Scenario, Previously Reported [Member]	Dec. 31, 2010 Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Deferred policy acquisition costs and present value of future profits	$ 3,094	$ 3,448	$ (1,150)	$ 1,200	$ 4,598	$ 4,900