Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value Disclosures [Abstract]

Financial Assets Carried at Fair Value

The financial assets carried at fair value were determined using the following inputs (in thousands):

	Balance at
	December 31,2017		(Level 1)		(Level 2)		(Level 3)
Cash equivalents:
Money market funds	$	110,299	$	110,299	$	—	$	—
Other assets:
Certificates of deposit	$	—	$	—	$	—	$	—

	Balance at
	December 31,2016		(Level 1)		(Level 2)		(Level 3)
Cash equivalents:
Money market funds	$	119,447	$	119,447	$	—	$	—
Other assets:
Certificates of deposit	$	530	$	—	$	530	$	—