Subsequent events (Details) - $ / shares			3 Months Ended		9 Months Ended
		Apr. 19, 2016	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Subsequent Event [Line Items]
Cash dividends declared on common stock (in dollars per share)	[1]		$ 0.0925	$ 0.0900	$ 0.2775	$ 0.2700
2016 Annual Dividend [Member]
Subsequent Event [Line Items]
Cash dividends declared on common stock (in dollars per share)					$ 0.37
Dividend Declared in Q3 2016 [Member]
Subsequent Event [Line Items]
Dividends payable, date declared					Apr. 19, 2016
Dividends payable, date of record					May 13, 2016
Dividends payable, date to be paid					Jun. 01, 2016
Subsequent Event [Member] | 2016 Annual Dividend [Member]
Subsequent Event [Line Items]
Cash dividends declared on common stock (in dollars per share)		$ 0.37
Subsequent Event [Member] | Dividend Declared in Q3 2016 [Member]
Subsequent Event [Line Items]
Cash dividends declared on common stock (in dollars per share)		$ 0.0925

[1] Share and per share data for 2015 have been adjusted for 2-for-1 stock split