Quarterly report pursuant to Section 13 or 15(d)

Equity - Exchangeable Shares and Series F and Series G Preferred Stock (Detail)

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Equity - Exchangeable Shares and Series F and Series G Preferred Stock (Detail)
3 Months Ended 6 Months Ended
Oct. 06, 2017
shares
Jun. 30, 2018
shares
Jun. 30, 2017
shares
Jun. 30, 2018
Acquisition
shares
Jun. 30, 2017
shares
Dec. 31, 2017
shares
Oct. 05, 2017
shares
Class of Stock [Line Items]              
Number of shares of Common stock received for each exchangeable share (in shares)       1      
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 (in shares)       50,000      
Number of business acquisitions having issuances of preferred stock | Acquisition       2      
Common stock, shares outstanding (in shares)   149,088,134   149,088,134   153,342,326  
Series F Preferred Stock              
Class of Stock [Line Items]              
Preferred stock, shares issued (in shares)             1
Preferred stock, shares retired (in shares) 1            
Series G Preferred Stock              
Class of Stock [Line Items]              
Preferred stock, shares issued (in shares)   1   1   1  
Preferred stock, shares outstanding (in shares)   1   1   1  
Exchangeable Shares For Common Stock              
Class of Stock [Line Items]              
Exchangeable shares exchanged for common stock (in shares)   0 0 0 2,500,000    
Exchangeable Shares              
Class of Stock [Line Items]              
Common stock, shares outstanding (in shares)   486,112   486,112   486,112  
Exchangeable Shares Associated with Series G Preferred Stock              
Class of Stock [Line Items]              
Common stock, shares outstanding (in shares)   400,000   400,000