Stock-Based Compensation (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 0 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Total payments for employees' tax obligations $ 2.6 $ 0  
PSUs      
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]      
Percent of target shares earned     200.00%
Shares withheld to satisfy tax withholding obligation 0.2    
Total payments for employees' tax obligations $ 2.6