Revenue recognition - Revenue by geographic region (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Disaggregation of Revenue [Line Items]
Revenues from contracts	$ 3,497,974	$ 3,472,045	$ 6,832,485	$ 6,951,339
North America
Disaggregation of Revenue [Line Items]
Revenues from contracts	2,344,338	2,248,806	4,600,089	4,494,897
Europe
Disaggregation of Revenue [Line Items]
Revenues from contracts	652,586	714,550	1,291,724	1,440,860
Asia Pacific
Disaggregation of Revenue [Line Items]
Revenues from contracts	463,840	465,974	861,554	927,614
Latin America
Disaggregation of Revenue [Line Items]
Revenues from contracts	$ 37,210	$ 42,715	$ 79,118	$ 87,968