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Stock-based Compensation - Summary of Activity in the Trust's Restricted Share Units (Details)
6 Months Ended
Jun. 30, 2017
$ / shares
shares
Dec. 31, 2016
shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Common stock, shares issued (in shares) 157,677,566 135,966,013
2013 Plan | Executive Awards, Restricted Stock Units (RSUs)    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Common stock, shares issued (in shares) 105,792  
Restricted stock shares issued net of tax withholdings (in shares) 50,112  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]    
Non-vested at the beginning of the period (in shares) 235,483  
Granted (in shares) 174,320  
Vested (in shares) (55,680)  
Non-vested at the end of the period (in shares) 354,123  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]    
Non-vested at beginning of period (in dollars per share) | $ / shares $ 21.84  
Granted (in dollars per share) | $ / shares 29.34  
Vested (in dollars per share) | $ / shares 16.94  
Non-vested at end of period (in dollars per share) | $ / shares $ 26.30  
2013 Plan | Trustee Awards, Restricted Stock Units (RSUs)    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]    
Non-vested at the beginning of the period (in shares) 57,260  
Granted (in shares) 32,831  
Vested (in shares) (38,871)  
Non-vested at the end of the period (in shares) 51,220  
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]    
Non-vested at beginning of period (in dollars per share) | $ / shares $ 17.03  
Granted (in dollars per share) | $ / shares 19.80  
Vested (in dollars per share) | $ / shares 16.72  
Non-vested at end of period (in dollars per share) | $ / shares $ 19.04