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Long-Term Debt - Convertible Senior Notes Dues 2032 (Details) - USD ($)
$ / shares in Units, $ in Thousands
 1 Months Ended 12 Months Ended
Nov. 30, 2016
Jul. 31, 2016
Mar. 31, 2012
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Nov. 01, 2016
Jun. 30, 2016
Debt Instrument [Line Items]                
Principal amount       $ 657,024        
Unamortized debt discount       19,094        
Loss on repurchase of long-term debt       (3,540) $ 0 $ 0    
Convertible Senior Notes Maturing March 2032 [Member]                
Debt Instrument [Line Items]                
Principal amount     $ 200,000 60,115 200,000      
Interest rate (as a percent)     3.25%          
Frequency of periodic payment     semi-annually          
Maturity date     Mar. 15, 2032          
Initial conversion ratio     0.0399752          
Initial conversion price per share (in dollars per share)     $ 25.02          
Redemption price as a percentage of principal amount     100.00%          
Repurchase price as a percentage of principal amount     100.00%          
Expected life used to estimate fair value     6 years          
Effective interest rate (as a percent)     6.90%          
Carrying amount of equity component     $ 22,500          
Unamortized debt discount     $ 35,400 2,581 $ 14,963      
Repurchased principal amount   $ 7,600         $ 125,000 $ 7,300
Repurchase amount   7,000           $ 6,500
Accrued interest included in repurchase amount $ 500 $ 100            
Loss on repurchase of long-term debt       (3,500)        
Amortization of debt issuance costs and discounts       7,500        
Re-acquisition of equity component       $ 2,500