Quarterly report pursuant to Section 13 or 15(d)

Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Details)

v3.3.0.814
Share-Based Compensation and Cash-Based Incentive Compensation - Additional Information (Details) - USD ($)
$ / shares in Units, $ in Millions
1 Months Ended 3 Months Ended 12 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Dec. 31, 2013
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Common stock available for award under plans 4,752,766   4,752,766      
Directors Compensation Plan            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Number of shares granted     0      
Common stock available for award under plans 500,564   500,564      
Restricted Stock Units (RSUs)            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Number of shares granted     0      
Performance based awards, percentage         100.00% 100.00%
Number of shares forfeited     49,541      
Number of shares vested     0 0    
Expected volatility, minimum           30.00%
Expected volatility, maximum           63.00%
Shares granted, grant date fair value       $ 19.4    
Unrecognized share-based compensation expense $ 13.7   $ 13.7      
Recognition period for unrecognized compensation expense     2016-11      
Restricted Stock Units (RSUs) | London Interbank Offered Rate (LIBOR)            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Risk-free interest rate, minimum           0.27%
Risk-free interest rate, maximum           0.91%
Restricted Stock Units (RSUs) | Minimum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Expected dividend yield           0.00%
Correlation of movement of total shareholder return           (84.00%)
Restricted Stock Units (RSUs) | Maximum            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Expected dividend yield           3.10%
Correlation of movement of total shareholder return           95.00%
CEO's 2014 Award | Chief Executive Officer            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Common stock, price per share $ 14.66   $ 14.66      
Number of shares issued 37,316          
Performance based awards, percentage 100.00%          
CEO's 2013 Award | Chief Executive Officer            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Common stock, price per share   $ 14.84   $ 14.84    
Number of shares issued   42,547        
Performance based awards, percentage   100.00%        
Restricted Shares            
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]            
Number of shares granted     0 0    
Number of shares forfeited     0 0    
Number of shares vested     0 0    
Unrecognized share-based compensation expense $ 0.4   $ 0.4      
Recognition period for unrecognized compensation expense     2017-04