Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2019

Summary of Significant Accounting Policies [Abstract]

Cash and Available-for-Sale Securities Adjusted Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value by Significant Investment Category

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 June 30, 2019, and December 31, 2018.

	June 30, 2019
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Fair Value		Cash and Cash Equivalents		Investments Available for Sale
Cash	$	3,509	$	—	$	—	$	3,509	$	3,509	$	—
Level 1:
Mutual funds		646		—		—		646		646		—
U.S. agency securities		2,771		1		—		2,772		—		2,772
Total investments		3,417		1		—		3,418		646		2,772
Total	$	6,926	$	1	$	—	$	6,927	$	4,155	$	2,772

	December 31, 2018
	Adjusted Cost		Unrealized Gains		Unrealized Losses		Fair Value		Cash and Cash Equivalents		Investments Available for Sale
Cash	$	5,048	$	—	$	—	$	5,048	$	5,048	$	—
Level 1:
Mutual funds		1,107		—		—		1,107		1,107		—
U.S. agency securities		3,259		—		—		3,259		1,456		1,803
Total investments		4,366		—		—		4,366		2,563		1,803
Total	$	9,414	$	—	$	—	$	9,414	$	7,611	$	1,803