Earnings per share - Computation of earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net income attributable to common shareholders	$ 338,898	$ 375,711
Denominator:
Basic - weighted average common shares (in shares)	128,463,992	132,361,654
Increase in weighted average common shares from dilutive effect of equity-based awards (in shares)	1,666,084	2,302,842
Diluted - weighted average common shares, assuming exercise of equity-based awards (in shares)	130,130,076	134,664,496
Basic earnings per share (in USD per share)	$ 2.64	$ 2.84
Diluted earnings per share (in USD per share)	$ 2.60	$ 2.79