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Equity (Exchangeable Shares and Series F and Series G Preferred Stock) - Additional Information (Detail) - shares
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Class of Stock [Line Items]      
Minimum number of shares that can be exchanged by exchangeable shareholders unless the number of remaining exchangeable shares registered in the name of the holder is less 50,000    
Number of shares of Common stock received for each exchangeable share 1    
Common stock, shares outstanding 144,710,773 152,907,166  
Common Stock [Member]      
Class of Stock [Line Items]      
Exchangeable shares exchanged for common stock 360,589 449,929 0
Series F Preferred Stock [Member]      
Class of Stock [Line Items]      
Number of preferred Stock issued to voting trust 1 1  
Series G Preferred Stock [Member]      
Class of Stock [Line Items]      
Number of preferred Stock issued to voting trust 1 1  
Exchangeable Shares [Member]      
Class of Stock [Line Items]      
Exchangeable shares exchanged for common stock (360,589) (449,929)  
Common stock, shares outstanding 6,515,453 6,876,042  
Series F- and Series G- Preferred Stock [Member]      
Class of Stock [Line Items]      
Exchangeable stock shares outstanding 3,900,000