Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2019

Financial Instruments

Schedule of available-for-sale securities

	September 30, 2019								December 31, 2018
	Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value		Amortized Cost		Gross Unrealized Gain		Gross Unrealized Loss		Estimated Fair Value
	(in thousands)
Money market deposits	$	5,666	$	—	$	—	$	5,666	$	26,539	$	—	$	—	$	26,539
U.S. Treasury securities		130,913		794		(72)		131,635		76,061		29		(405)		75,685
U.S. agency securities		7,000		—		—		7,000		13,017		—		(126)		12,891
Municipal securities		47,928		161		(24)		48,065		18,935		7		(57)		18,885
Total	$	191,507	$	955	$	(96)	$	192,366	$	134,552	$	36	$	(588)	$	134,000
Classified as:
Cash equivalents							$	5,666							$	26,539
Short-term investments								186,700								107,461
Total							$	192,366							$	134,000

Summarized portfolio of available-for-sale securities by contractual maturity

	September 30, 2019
	Amortized Cost		Fair Value
	(in thousands)
Less than one year	$	86,161	$	86,343
Greater than one year but less than five years		99,680		100,357
Total	$	185,841	$	186,700