Subsequent events (Details) - $ / shares		12 Months Ended
	Jul. 21, 2015	Jun. 30, 2015	Jun. 30, 2014
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)		$ 0.72	$ 0.70
2015 Q4 Dividend [Member]
Subsequent Event [Line Items]
Dividends payable, date declared		Jul. 21, 2015
Dividends payable, date of record		Aug. 14, 2015
Dividends payable, date paid		Aug. 31, 2015
Subsequent Event [Member] | 2015 Q4 Dividend [Member]
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)	$ 0.185
Subsequent Event [Member] | 2015 Annual Dividend [Member]
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)	0.72
Subsequent Event [Member] | 2016 Annual Dividend [Member]
Subsequent Event [Line Items]
Common stock, dividends declared (in dollars per share)	$ 0.74