Financial Instruments and Fair Value Measurements - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Transfers between level 1 and level 2, assets	$ 0	$ 0
Transfers between level 2 and level 1, assets	0	0
Transfers between level 1 and level 2, liabilities	0	0
Transfers between level 2 and level 1, liabilities	0	0
Transfer of assets into level 3	0	0
Transfer of assets out of level 3	0	0
Transfer of liabilities into level 3	0	0
Transfer of liabilities out of level 3	0	0
Convertible senior notes	282,082	282,082	$ 281,126
Convertible Senior Notes.
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Convertible senior notes	282,100	282,100
Convertible Senior Notes. | Fair Value, Inputs, Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Convertible senior notes, fair value	$ 444,200	$ 444,200