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Operations and Summary of Significant Accounting Policies - Stock Repurchase Program (Details) - USD ($)
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2016
Dec. 31, 2015
Mar. 31, 2016
2015 Stock Repurchase Program              
Accelerated Share Repurchases [Line Items]              
Common stock repurchase, authorized amount $ 50,000,000.0   $ 50,000,000.0     $ 50,000,000.0 $ 50,000,000.0
Repurchase of common stock (in shares)   689,184       1,338,894  
Settlement of accelerated share repurchase program   $ (25,000,000)   $ (25,000,000)   $ (47,100,000)  
Stock repurchase, average cost per share (in USD per share)       $ 36.27   $ 35.21  
2016 Stock Repurchase Program              
Accelerated Share Repurchases [Line Items]              
Common stock repurchase, authorized amount         $ 125,000,000.0    
Repurchase of common stock (in shares) 1,137,656       1,244,003    
Settlement of accelerated share repurchase program $ (50,000,000)   $ (50,000,000)   $ (53,500,000)    
Stock repurchase, average cost per share (in USD per share)     $ 43.95   $ 43.01