Significant Accounting Policies - Investment and other assets (Details) - USD ($) $ in Thousands	12 Months Ended
Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018
Schedule of Equity Method Investments [Line Items]
Investment in joint-venture companies and company's equity in undistributed earnings	$ 317,975	$ 316,728
Share of earnings from investments in joint-venture companies	$ 74,517	$ 93,239	$ 50,473
Maximum
Schedule of Equity Method Investments [Line Items]
Ownership percentage (or less)	50.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of income (loss) for proportionate share of equity method investee's income (loss).

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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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