Summary of Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2021

Summary of Significant Accounting Policies [Abstract]

Adjusted Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value of Financial Assets

The following tables show the adjusted cost, gross unrealized gains, gross unrealized losses and fair value of our securities by significant investment category as of March 31, 2021 and December 31, 2020.

	March 31, 2021
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Fair Value		Cash and Cash Equivalents		Investments Available for Sale
Cash	$	83,156	$	—	$	—	$	83,156	$	83,156	$	—
Level 1:
Mutual funds		114,042		—		—		114,042		114,042		—
U.S. agency securities		12,718		4		—		12,722		—		12,722
U.S. treasury securities		7,110		3		—		7,113		—		7,113
		133,870		7		—		133,877		114,042		19,835
Total	$	217,026	$	7	$	—	$	217,033	$	197,198	$	19,835

	December 31, 2020
	Adjusted Cost		Unrealized Gains		Unrealized Losses			Fair Value		Cash and Cash Equivalents		Investments Available for Sale
Cash	$	121,785	$	—	$	—		$	121,785	$	121,785	$	—
Level 1:
Mutual funds		70,996		—		—			70,996		70,996		—
U.S. agency securities		13,767		2		—			13,769		127		13,642
U.S. treasury securities		14,707		—		(1	)		14,706		—		14,706
		99,470		2		(1	)		99,471		71,123		28,348
Total	$	221,255	$	2	$	(1	)	$	221,256	$	192,908	$	28,348