Stock repurchase program (Details) (USD $)	6 Months Ended				0 Months Ended	6 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2012 Additional paid-in capital	Dec. 31, 2012 Retained earnings	Oct. 23, 2012 Current stock repurchase program	Dec. 31, 2012 Current stock repurchase program	Dec. 31, 2012 Previous stock repurchase program
Stockholders Equity Note [Line Items]
Authorized amount for stock repurchases					$ 20,000,000
Payments for repurchase of common stock	12,004,000	9,294,000				8,300,000	3,700,000
Number of treasury shares acquired						1,070,089	615,103
Final price paid per share						$ 7.71	$ 6.10
Remaining authorized repurchase amount						11,700,000
Repurchase shares of common stock			$ 5,400,000	$ 6,600,000