Subsequent events - Narrative (Details) (USD $)	0 Months Ended	3 Months Ended		9 Months Ended		0 Months Ended	3 Months Ended
	Jan. 21, 2014	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014	Mar. 31, 2013	Apr. 15, 2014 Subsequent Event [Member]	Mar. 31, 2014 Subsequent Event [Member]
Dividends Payable, Date Declared		Jan. 21, 2014					Apr. 15, 2014
Common Stock, Dividends, Per Share, Declared (in dollars per share)	$ 0.175	$ 0.175	$ 0.175	$ 0.525	$ 0.525	$ 0.175
Annual Dividend Rate Per Share (in dollars per share)	$ 0.70					$ 0.70
Dividends Payable, Date of Record	Feb. 14, 2014					May 15, 2014
Dividends Payable, Date to be Paid	Feb. 28, 2014					May 30, 2014