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Employee Benefit Plans - Narrative (Details) - USD ($)
$ in Millions
1 Months Ended 3 Months Ended 9 Months Ended
Jan. 31, 2017
Feb. 29, 2016
Sep. 30, 2017
Sep. 30, 2016
Sep. 30, 2017
Sep. 30, 2016
Dec. 31, 2016
2005 Incentive Plan [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares available for issuance (in shares)     2,400,000   2,400,000    
Restricted Stock [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation     $ 1.7 $ 1.4 $ 5.4 $ 4.3  
Performance Share Units [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Share-based compensation     4.0 $ 2.5 5.8 $ 5.3  
Share-based award liability     $ 10.2   $ 10.2   $ 7.1
Cash paid to settle share-based award liability $ 0.6            
ESPP [Member]              
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]              
Shares available for issuance (in shares)     600,000   600,000    
Shares authorized for issuance (in shares)     1,500,000   1,500,000    
Purchase limit per employee (in shares)   130