Financial Instruments (Tables)

3 Months Ended

Mar. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Summary of Investment in Cash Equivalents and Marketable Securities

Cash equivalents and marketable securities, consisted of the following:

	March 31, 2017
	Amortized Cost		Unrealized Gains (Losses)			Fair Value
	(Dollars in thousands)
Cash equivalents:
Money market funds	$	80,310	$	—		$	80,310
Marketable securities:
Corporate bonds		15,681		(120	)		15,561
Commercial paper		4,995		—			4,995
U.S. treasury securities		7,489		8			7,497
	$	108,475	$	(112	)	$	108,363
Due within one year						$	105,860
Due within two years							2,503
Total						$	108,363
	December 31, 2016
	Amortized Cost		Unrealized Gains (Losses)			Fair Value
	(Dollars in thousands)
Cash equivalents:
Money market funds	$	75,375	$	—		$	75,375
Marketable securities:
Corporate bonds		15,681		(96	)		15,585
Commercial paper		4,977		10			4,987
U.S. treasury securities		7,489		10			7,499
U.S. agency obligations		2,497		3			2,500
	$	106,019	$	(73	)	$	105,946
Due within one year						$	98,452
Due within two years							7,494
Total						$	105,946

Summary of Financial Assets Measured at Fair Value on a Recurring Basis

The following tables present information about our financial assets that are measured at fair value on a recurring basis and indicates the fair value hierarchy of the valuation techniques utilized to determine such fair value:

	March 31, 2017
	Level 1		Level 2		Level 3		Total
	(Dollars in thousands)
Assets:
Cash and cash equivalents:
Money market funds	$	80,310	$	—	$	—	$	80,310
Marketable securities:
Corporate bonds		—		15,561		—		15,561
Commerical paper		—		4,995		—		4,995
U.S. treasury securities		—		7,497		—		7,497
Total	$	80,310	$	28,053	$	—	$	108,363
	December 31, 2016
	Level 1		Level 2		Level 3		Total
	(Dollars in thousands)
Assets:
Cash and cash equivalents:
Money market funds	$	75,375	$	—	$	—	$	75,375
Marketable securities:
Corporate bonds		—		15,585		—		15,585
Commerical paper		—		4,987		—		4,987
U.S. treasury securities		—		7,499		—		7,499
U.S. agency obligations		—		2,500		—		2,500
Total	$	75,375	$	30,571	$	—	$	105,946