Marketable Securities (Tables)

12 Months Ended

Dec. 31, 2019

Marketable Securities [Abstract]

Schedule of Marketable Securities by Category

At December 31, 2019 and 2018, marketable securities are categorized as follows:

	Amortized Cost		Gross Unrealized Holding Gains		Gross Unrealized Holding Losses		Fair Value
December 31, 2019
Municipal notes and bonds	$	80,926	$	188	$	6	$	81,108
Asset-backed securities		10,767		12		—		10,779
Certificates of deposit		30,500		7		—		30,507
Commercial paper		30,707		1		—		30,708
Corporate bonds		36,409		52		—		36,461
Total marketable securities	$	189,309	$	260	$	6	$	189,563
December 31, 2018
Municipal notes and bonds	$	62,681	$	43	$	40	$	62,684
Total marketable securities	$	62,681	$	43	$	40	$	62,684

Schedule of Amortized Cost and Estimated Fair Value of Marketable Securities Classified by Maturity Date

The amortized cost and estimated fair value of marketable securities classified by the maturity date listed on the security, regardless of the Consolidated Balance Sheet classification, is as follows at December 31, 2019 and 2018:

	December 31, 2019				December 31, 2018
	Amortized Cost		Fair Value		Amortized Cost		Fair Value
Due within one year	$	152,649	$	152,852	$	47,767	$	47,732
Due after one through five years		36,660		36,711		14,914		14,952
Due after five through ten years		—		—		—		—
Due after ten years		—		—		—		—
Total marketable securities	$	189,309	$	189,563	$	62,681	$	62,684

Summary of Estimated Fair Value and Gross Unrealized Holding Losses of Marketable Securities in Unrealized Loss Position

The following table summarizes the estimated fair value and gross unrealized holding losses of marketable securities, aggregated by investment instrument and period of time in an unrealized loss position, at December 31, 2019 and 2018.

	In Unrealized Loss Position For Less Than 12 Months				In Unrealized Loss Position For Greater Than 12 Months
	Fair Value		Gross Unrealized Losses		Fair Value		Gross Unrealized Losses
December 31, 2019
Municipal notes and bonds	$	14,166	$	6	$	—	$	—
Total marketable securities	$	14,166	$	6	$	—	$	—
December 31, 2018
Municipal notes and bonds	$	27,952	$	30	$	4,671	$	10
Total marketable securities	$	27,952	$	30	$	4,671	$	10