Annual report pursuant to Section 13 and 15(d)

Financing Arrangements - Summary of Debt (Details)

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Financing Arrangements - Summary of Debt (Details) - USD ($)
$ in Thousands
Mar. 08, 2018
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2016
Feb. 28, 2015
Debt Instrument [Line Items]          
Debt   $ 660,200      
Unamortized bond discounts, fair value adjustments and issue costs, net   (41,136)   $ (26,979)  
Total carrying value of debt   619,064   470,300  
Less: current portion, net   (20,106)   (2,069)  
Total noncurrent debt   598,958   468,231  
Bank term loans          
Debt Instrument [Line Items]          
Debt   490,625      
Convertible subordinated notes          
Debt Instrument [Line Items]          
Debt   $ 82,500 $ 82,500 82,500  
Stated interest rate   2.75% 2.75%   2.75%
Other debt          
Debt Instrument [Line Items]          
Debt   $ 9,075   3,299  
Revolving Credit Facility          
Debt Instrument [Line Items]          
Debt   78,000      
First Lien Credit Agreement | Bank term loans          
Debt Instrument [Line Items]          
Debt   0   263,980  
First Lien Credit Agreement | Revolving Credit Facility          
Debt Instrument [Line Items]          
Debt   0   55,500  
Second Lien Credit Agreement | Bank term loans          
Debt Instrument [Line Items]          
Debt   $ 0   $ 92,000  
Subsequent Event | Convertible subordinated notes          
Debt Instrument [Line Items]          
Stated interest rate 2.75%