Available-for-Sale Investments (Tables)

12 Months Ended

Dec. 31, 2018

Investments Debt And Equity Securities [Abstract]

Summary of Available-for-Sale Securities Held

The following tables summarize the available-for-sale securities held at December 31, 2018 and 2017 (in thousands):

December 31, 2018	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Corporate debt securities	$	107,571	$	4	$	(70	)	$	107,505
U.S. government agency securities	$	3,971	$	1	$	—		$	3,972
Total	$	111,542	$	5	$	(70	)	$	111,477
December 31, 2017	Amortized cost		Gross unrealized gains		Gross unrealized losses			Fair Value
Corporate debt securities	$	28,593	$	1	$	(9	)	$	28,585
Total	$	28,593	$	1	$	(9	)	$	28,585