Financial Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Apr. 17, 2014	Feb. 28, 2013	Aug. 01, 2011
3.75% Convertible Notes
Fair value measurement
Interest rate (as a percent)	3.75%	3.75%			3.75%
3.50% Convertible Notes
Fair value measurement
Interest rate (as a percent)	3.50%	3.50%		3.50%
3.50% Series A Convertible Notes
Fair value measurement
Interest rate (as a percent)	3.50%	3.50%	3.50%
Non-recurring basis | Carrying Value
Fair value measurement
Long term debt	$ 204,773	$ 202,853
Non-recurring basis | Carrying Value | 3.75% Convertible Notes
Fair value measurement
Long term debt	95,134	93,739
Non-recurring basis | Carrying Value | 3.50% Convertible Notes
Fair value measurement
Long term debt	44,654	44,654
Non-recurring basis | Carrying Value | 3.50% Series A Convertible Notes
Fair value measurement
Long term debt	64,985	64,460
Non-recurring basis | Fair Value
Fair value measurement
Long term debt	228,195	270,635
Non-recurring basis | Fair Value | 3.75% Convertible Notes
Fair value measurement
Long term debt	100,910	102,645
Non-recurring basis | Fair Value | 3.50% Convertible Notes
Fair value measurement
Long term debt	49,424	65,230
Non-recurring basis | Fair Value | 3.50% Series A Convertible Notes
Fair value measurement
Long term debt	$ 77,861	$ 102,760