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Stock Incentive Plans - Performance Stock Units (Details) - Performance Stock Units - $ / shares
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Stock of common stock earned for the PSUs vested in 2016 (as a percent) 89.50%    
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]      
Number of shares, Beginning Balance 676,359 436,170 223,176
Number of shares, Granted 310,398 218,467 200,685
Number of shares, Additional shares from dividends 38,324 21,722 12,309
Number of shares, Vested (242,096)    
Number of shares, Forfeited (96,301)    
Number of shares, Ending Balance 686,684 676,359 436,170
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]      
Weighted-average grant date fair value, Beginning balance (in dollars per share) $ 11.41 $ 10.95 $ 9.66
Weighted-average grant date fair value, Granted (in dollars per share) 8.54 12.13 12.33
Weighted-average grant date fair value, Additional shares from dividends (in dollars per share) 9.37 13.51 12.01
Weighted-average grant date fair value, Vested (in dollars per share) 9.85    
Weighted-average grant date fair value, Forfeited (in dollars per share) 10.74    
Weighted-average grant date fair value, Ending balance (in dollars per share) $ 10.65 $ 11.41 $ 10.95