Quarterly report pursuant to Section 13 or 15(d)

Basis of Financial Statement Presentation - Fair Value Measurements (Details)

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Basis of Financial Statement Presentation - Fair Value Measurements (Details) - USD ($)
$ in Thousands
Sep. 30, 2018
Mar. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money markets, Carrying Value $ 70,580 $ 83,891
Total debt, Carrying Value (316,637) (324,623)
Certificates of Deposit, at carrying value 27,500 33,900
Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt, Fair Value (334,194) (343,125)
Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt, Fair Value 0 0
Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt, Fair Value (334,194) (343,125)
Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total debt, Fair Value 0 0
Money markets | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money markets, Fair Value Measurement 70,580 83,891
Money markets | Level 1 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money markets, Fair Value Measurement 70,580 83,891
Money markets | Level 2 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money markets, Fair Value Measurement 0 0
Money markets | Level 3 | Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Money markets, Fair Value Measurement $ 0 $ 0