Subsequent Event (Details) - USD ($) $ in Thousands	Aug. 07, 2017	Jun. 30, 2017
Subsequent Event
Outstanding debt		$ 164,571
Existing 3.50% Convertible Notes
Subsequent Event
Interest rate (as a percent)	3.50%	3.50%
Subsequent Event | 3.75% Convertible Senior Notes due 2022
Subsequent Event
Aggregate principal amount of debt issued	$ 85,000
Interest rate (as a percent)	3.75%
Subsequent Event | 3.75% Convertible Senior Notes due 2022 | Debt Conversion with Existing Convertible Notes
Subsequent Event
Aggregate principal amount of debt issued	$ 53,000
Subsequent Event | 3.75% Convertible Senior Notes due 2022 | Debt Conversion with Qualified New Investors
Subsequent Event
Aggregate principal amount of debt issued	32,000
Subsequent Event | Existing 3.50% Convertible Notes
Subsequent Event
Aggregate principal amount of debt issued	47,000
Repurchase of additional existing notes	28,000
Outstanding debt	$ 40,000