CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, shares authorized	1,250,000,000	1,250,000,000
Common shares, shares issued	305,475,256	303,757,574
Treasury shares	92,788,323	81,814,591
Consolidated Investment Entities:
Receivables, fair value (in dollars)	$ 23	$ 39
Debt, fair value (in dollars)	4,726	4,712
Other liabilities, fair value (in dollars)	$ 75	$ 85