Earnings per share - Reconciliation of Numerator and Denominator of Basic and Diluted Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Numerator:
Net income attributable to common shareholders	$ 365,989	$ 238,673	$ 707,545	$ 690,107
Denominator:
Basic - weighted average common shares (in shares)	133,032,431	133,232,378	133,107,321	133,410,622
Increase in weighted average common shares from dilutive effect of equity-based awards (in shares)	2,735,849	2,870,596	2,554,064	2,116,573
Diluted - weighted average common shares, assuming exercise of equity-based awards (in shares)	135,768,280	136,102,974	135,661,385	135,527,195
Basic earnings per share (in USD per share)	$ 2.75	$ 1.79	$ 5.32	$ 5.17
Diluted earnings per share (in USD per share)	$ 2.70	$ 1.75	$ 5.22	$ 5.09