CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Millions		Dec. 31, 2017	Dec. 31, 2016
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		327,506,935	324,006,315
Treasury shares		180,872,271	169,246,411
Consolidated investment entities [Member]
Receivables, fair value (in dollars)		$ 25	$ 11
Other assets, fair value (in dollars)		0	0
Debt, fair value (in dollars)	[1]	2,208	2,319
Other liabilities, fair value (in dollars)		$ 63	$ 95

[1] The carrying value of the CLOs’ debt is set equal to the fair value of the CLOs’ assets. The estimated fair value of the CLOs’ debt was $2.2 billion and $2.3 billion as of December 31, 2017 and December 31, 2016, respectively.