Cash Equivalents and Short-Term Investments - Schedule of Investments' Gross Unrealized Loss and Fair Value, Aggregated by Investment Category (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 41,593	$ 20,553
Unrealized Loss, Less than 12 Months	(29)	(10)
Fair Value More than, 12 Months	0	0
Unrealized Loss, More than 12 Months	0	0
Fair Value, Total	41,593	20,553
Unrealized Loss, Total	(29)	(10)
Corporate Securities
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	19,578	16,539
Unrealized Loss, Less than 12 Months	(23)	(8)
Fair Value More than, 12 Months	0	0
Unrealized Loss, More than 12 Months	0	0
Fair Value, Total	19,578	16,539
Unrealized Loss, Total	(23)	(8)
U.S. Government Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Fair Value, Less than 12 Months	22,015	4,014
Unrealized Loss, Less than 12 Months	(6)	(2)
Fair Value More than, 12 Months	0	0
Unrealized Loss, More than 12 Months	0	0
Fair Value, Total	22,015	4,014
Unrealized Loss, Total	$ (6)	$ (2)