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		9 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019	Mar. 31, 2018
Cross-currency swap contracts
Derivative Instruments, Gain (Loss)
Derivative and non derivative instruments gain (loss) recognized in accumulated other comprehensive income (loss)	$ 6,748	$ (13,374)	$ 14,367	$ (22,672)
Foreign denominated debt
Derivative Instruments, Gain (Loss)
Derivative and non derivative instruments gain (loss) recognized in accumulated other comprehensive income (loss)	$ 13,287	$ (15,423)	$ 24,558	$ (43,150)