Earnings per share - Computation of earnings per share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income attributable to common shareholders	$ 204,474	$ 311,737	$ 543,372	$ 687,448
Denominator:
Basic - weighted average common shares (in shares)	128,396,933	130,361,273	128,430,463	131,361,464
Increase in weighted average common shares from dilutive effect of equity-based awards (in shares)	2,098,448	1,949,937	1,723,616	2,088,210
Diluted - weighted average common shares, assuming exercise of equity-based awards (in shares)	130,495,381	132,311,210	130,154,079	133,449,674
Basic earnings per share (in USD per share)	$ 1.59	$ 2.39	$ 4.23	$ 5.23
Diluted earnings per share (in USD per share)	$ 1.57	$ 2.36	$ 4.17	$ 5.15