Hardy (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Jul. 03, 2012	Sep. 30, 2012 Hardy [Member]	Sep. 30, 2012 Hardy [Member]	Dec. 31, 2011 Hardy [Member]	Jul. 03, 2012 Hardy [Domain]
Business Acquisition [Line Items]
Gross written premiums								$ 430
Net income (loss) in accordance with IFRS								(55)
Business acquisition, cost of acquired entity, purchase price									231
Business combination, acquisition related costs							4
Amortization of deferred acquisition costs	333	297	937	880		18
Amortization expense included in other expenses						6
Future Amortization Expense, Remainder of Fiscal Year							19
Future amortization expense, year one							21
Future amortization expense, year two							4
Future amortization expense, year three							1
Future amortization expense, year four							2
Future amortization expense, year five							2
Business Acquisition, Purchase Price Allocation, Goodwill Amount					35
Carrying value of funds at Lloyd's	66		66
Carrying Value Of Securities Deposited Under Requirements Of Regulatory Authorities						$ 71	$ 71