CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
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	312,835,625	309,399,529
Treasury shares	110,369,527	105,456,535
Consolidated Investment Entities
Receivables, fair value (in dollars)	$ 111	$ 77
Debt, fair value (in dollars)	4,595	4,450
Other liabilities, fair value (in dollars)	$ 301	$ 166