Fair Value Measurements (Details)	3 Months Ended
	Sep. 30, 2020 USN ($)	Sep. 30, 2020 USD ($)	Jun. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)
Non-financial assets measured at fair value
Non-financial assets measured at fair value		$ 0	$ 0
Amortized Cost		26,352,000		$ 22,135,000
Gross Unrealized Loss		(1,000)		(24,000)
Gross Unrealized Gain		3,000		20,000
Estimated Fair Value		26,354,000		22,131,000
Other-than-temporary impairment of investments	$ 0
Level 1:
Non-financial assets measured at fair value
Amortized Cost		4,190,000		10,576,000
Gross Unrealized Loss				(1,000)
Estimated Fair Value		4,190,000		10,575,000
Level 1: | Money market funds
Non-financial assets measured at fair value
Amortized Cost		4,190,000		10,576,000
Gross Unrealized Loss				(1,000)
Estimated Fair Value		4,190,000		10,575,000
Level 2:
Non-financial assets measured at fair value
Amortized Cost		22,162,000		11,559,000
Gross Unrealized Loss		(1,000)		(23,000)
Gross Unrealized Gain		3,000		20,000
Estimated Fair Value		22,164,000		11,556,000
Level 2: | Commercial paper
Non-financial assets measured at fair value
Amortized Cost		10,197,000		1,495,000
Gross Unrealized Loss				(1,000)
Gross Unrealized Gain		1,000
Estimated Fair Value		10,198,000		1,494,000
Level 2: | Corporate notes and bonds
Non-financial assets measured at fair value
Amortized Cost		2,255,000		6,044,000
Gross Unrealized Loss				(22,000)
Gross Unrealized Gain		2,000
Estimated Fair Value		2,257,000		6,022,000
Level 2: | US Treasuries
Non-financial assets measured at fair value
Amortized Cost		9,710,000		3,013,000
Gross Unrealized Loss		(1,000)
Gross Unrealized Gain		0		20,000
Estimated Fair Value		$ 9,709,000		3,033,000
Level 2: | US Government agencies
Non-financial assets measured at fair value
Amortized Cost				1,007,000
Estimated Fair Value				$ 1,007,000