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Short-Term Investments (Tables)

6 Months Ended

Jun. 30, 2019

Short Term Investments [Abstract]

Summary of Short-Term Investments

The following is a summary of our short-term investments (in thousands):

		June 30, 2019
						Gross				Gross
		Amortized				Unrealized				Unrealized				Estimated
		Cost				Gains				Losses				Fair Value
U.S. treasury bills and government agency obligations		$	99,524			$	91			$	—			$	99,615
U.S. corporate debt securities			33,007				30				—				33,037
Foreign corporate debt securities			10,002				16				—				10,018
U.S. commercial paper			48,969				10				—				48,979
Foreign commercial paper			31,318				—				—				31,318
Total		$	222,820			$	147			$	—			$	222,967

		December 31, 2018
						Gross				Gross
		Amortized				Unrealized				Unrealized				Estimated
		Cost				Gains				Losses				Fair Value
U.S. treasury bills and government agency obligations		$	59,747			$	—			$	(6	)		$	59,741
U.S. corporate debt securities			59,164				—				(77	)			59,087
Foreign corporate debt securities			5,041				5				—				5,046
U.S. commercial paper			52,800				—				—				52,800
Foreign commercial paper			123,870				—				(9	)			123,861
Total		$	300,622			$	5			$	(92	)		$	300,535