Estimated Fair Value of Financial Instruments - Convertible Senior Notes (Details) - Convertible Senior Notes - Level 2 - USD ($) $ in Thousands	Sep. 30, 2018	Jun. 30, 2018
Carrying Amount
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible Senior Notes	$ 19,799	$ 19,763
Estimated Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Convertible Senior Notes	$ 79,424	$ 89,436

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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