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Nature of Business and Accounting Policies - Share-Based Compensation and Advertising Expense (Details) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Accounting Policies [Abstract]      
Percentage of employees eligible for acceleration of equity awards (less than) (percent) 5.00%    
Advertising Expenses $ 24.5 $ 16.2 $ 19.6