v3.8.0.1
Debt and Credit Facility Conversion Features (Details)
3 Months Ended 6 Months Ended
Sep. 30, 2017
USD ($)
$ / shares
Sep. 30, 2017
day
$ / shares
Jun. 30, 2017
USD ($)
2015 Senior Subordinated Convertible Debt      
Debt Instrument [Line Items]      
Debt instrument, convertible, if-converted value in excess of principal | $ $ 697,900,000    
2007 Junior Subordinated Convertible Debt      
Debt Instrument [Line Items]      
Debt instrument, convertible, threshold percentage of stock price trigger   130.00%  
Long-term debt, contingent payment of interest, percentage   0.50%  
Debt instrument, convertible, if-converted value in excess of principal | $ $ 48,600,000    
2007 Junior Subordinated Convertible Debt | Minimum      
Debt Instrument [Line Items]      
Long-term debt, contingent payment of interest, percentage   0.25%  
Debt instrument, convertible, trading price | $ / shares $ 400 $ 400  
2007 Junior Subordinated Convertible Debt | Maximum      
Debt Instrument [Line Items]      
Long-term debt, contingent payment of interest, percentage   0.50%  
Debt instrument, convertible, trading price | $ / shares $ 1,500 $ 1,500  
Convertible Debt | Debt Instrument, Redemption, Period One      
Debt Instrument [Line Items]      
Debt instrument, convertible, threshold percentage of stock price trigger   130.00%  
Debt instrument, convertible, threshold trading days   20  
Debt instrument, convertible, threshold consecutive trading days   30  
Convertible Debt | Debt Instrument, Redemption, Period Two      
Debt Instrument [Line Items]      
Debt instrument, convertible, threshold percentage of stock price trigger   98.00%  
Debt instrument, convertible, threshold trading days   5  
Debt instrument, convertible, threshold consecutive trading days   10  
Long-term Debt | 2007 Junior Subordinated Convertible Debt      
Debt Instrument [Line Items]      
Debt instrument, principal | $     $ 15,200,000.0