Consolidated Balance Sheets (Parenthetical)	Dec. 31, 2011	Dec. 31, 2010
Consolidated Balance Sheets [Abstract]
Common shares, shares authorized	1,400,000,000	1,400,000,000
Common shares, shares issued	347,900,000	348,600,000
Common shares, shares outstanding	347,900,000	348,600,000
Preferred shares, shares authorized	1,000,000	1,000,000
Preferred shares, shares issued
Preferred shares, shares outstanding