Financial instruments - Gain (losses) on derivative and non-derivative financial instruments recorded in accumulated other comprehensive (loss) (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2020	Dec. 31, 2019
Cross-currency swap contracts
Derivative Instruments, Gain (Loss) [Line Items]
Derivative and non-derivative instruments gain (loss) recognized in accumulated other comprehensive income (loss)	$ (21,729)	$ (3,833)	$ (38,863)	$ 6,551
Foreign denominated debt
Derivative Instruments, Gain (Loss) [Line Items]
Derivative and non-derivative instruments gain (loss) recognized in accumulated other comprehensive income (loss)	$ (26,109)	$ (16,600)	$ (51,836)	$ 8,324