CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $)	Dec. 31, 2011	Dec. 31, 2010
CONSOLIDATED BALANCE SHEETS
Common shares, par value (in dollars per share)	$ 0.01	$ 0.01
Common shares, authorized shares (in shares)	200,000,000	200,000,000
Common shares, issued shares (in shares)	95,068,457	94,416,477
Common shares, outstanding shares (in shares)	95,068,457	94,416,477