Deferred Compensation Plan - Available-for-sale Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jun. 30, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	$ 636	$ 704
Mutual funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	636	704
Recurring
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	636	704
Recurring | Mutual funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	636	704
Recurring | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	252	281
Recurring | Level 1 | Mutual funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	252	281
Recurring | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	384	423
Recurring | Level 2 | Mutual funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total short-term investments	$ 384	$ 423