Earnings per share - Computation of earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Numerator:
Net income attributable to common shareholders	$ 375,711	$ 285,397
Denominator:
Basic - weighted average common shares (in shares)	132,361,654	133,176,964
Increase in weighted average common shares from dilutive effect of equity-based awards (in shares)	2,302,842	2,617,306
Diluted - weighted average common shares, assuming exercise of equity-based awards (in shares)	134,664,496	135,794,270
Basic earnings per share (in USD per share)	$ 2.84	$ 2.14
Diluted earnings per share (in USD per share)	$ 2.79	$ 2.10