Convertible 3.75% Senior Notes (Details 2) - Convertible Notes Payable [Member] - USD ($) $ in Thousands		6 Months Ended
	Dec. 31, 2014	Jun. 30, 2015
Debt Instrument [Line Items]
Fair Value of Convertible Feature of Convertible 3.75% Senior Notes, Initial Measurement Beginning balance	$ 43,700	$ 41,400
Fair Value of Convertible Feature of Convertible 3.75% Senior Notes, Decrease in Fair Value	2,300	23,144
Fair Value of Convertible Feature of Convertible 3.75% Senior Notes, Reclassification of derivative liability to equity		18,256
Fair Value of Convertible Feature of Convertible 3.75% Senior Notes, Ending balance	$ 41,400	$ 0