Subsequent events (Details) (USD $)	3 Months Ended		9 Months Ended		0 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Mar. 31, 2015	Mar. 31, 2014	Apr. 21, 2015
Subsequent Event [Line Items]
Common stock, dividends, per share, declared (in dollars per share)	$ 0.180	$ 0.175	$ 0.540	$ 0.525
Subsequent Event [Member] | Dividend Declared 2014 Q3 [Member]
Subsequent Event [Line Items]
Dividends payable, date declared			Apr. 21, 2015
Common stock, dividends, per share, declared (in dollars per share)					$ 0.18
Dividends payable, date of record			May 15, 2015
Dividends payable, date to be paid			May 29, 2015
Subsequent Event [Member] | Dividend Declared 2015 Annual [Member]
Subsequent Event [Line Items]
Annual dividend rate per share (in dollars per share)			$ 0.72