Financial Instruments (Details 2) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Aug. 02, 2011	Aug. 01, 2011	Feb. 28, 2013	Apr. 17, 2014	Jun. 30, 2014
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% Series A Convertible Notes
Fair value measurement
Interest rate (as a percent)					3.50%
Non-recurring basis | Carrying Value
Fair value measurement
Long term debt	200,989					$ 195,612
Non-recurring basis | Carrying Value | 3.75% Convertible Notes
Fair value measurement
Long term debt	92,390					88,511
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	63,945					62,447
Non-recurring basis | Fair Value
Fair value measurement
Long term debt	315,452					319,868
Non-recurring basis | Fair Value | 3.75% Convertible Notes
Fair value measurement
Long term debt	111,580					115,415
Non-recurring basis | Fair Value | 3.50% Convertible Notes
Fair value measurement
Long term debt	79,163					79,388
Non-recurring basis | Fair Value | 3.50% Series A Convertible Notes
Fair value measurement
Long term debt	124,709					$ 125,065