Senior Convertible Notes (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Senior Convertibles Notes [Line Items]
Senior Convertible Notes, net of unamortized discount and deferred financing costs	$ 159,721		$ 157,263
1.50% Senior Convertible Notes Due 2021 [Member]
Senior Convertibles Notes [Line Items]
Senior Convertible Notes, principal amount	$ 172,500		172,500
Senior Convertible Notes, interest rate, stated percentage	1.50%
Senior Convertible Notes, interest expense	$ 2,900	$ 2,700
Senior Convertible Notes, unamortized debt discount	(11,633)		(13,861)
Senior Convertible Notes, unamortized deferred financing costs	(1,146)		(1,376)
Senior Convertible Notes, net of unamortized discount and deferred financing costs	$ 159,721		$ 157,263