Marketable Securities - Summary of Estimated Fair Value and Gross Unrealized Holding Losses of Marketable Securities in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
In Unrealized Loss Position For Less Than 12 Months, Fair Value	$ 14,166	$ 27,952
In Unrealized Loss Position For Less Than 12 Months, Gross Unrealized Losses	6	30
In Unrealized Loss Position For Greater Than 12 Months, Fair Value	0	4,671
In Unrealized Loss Position For Greater Than 12 Months, Gross Unrealized Losses	0	10
Municipal notes and bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
In Unrealized Loss Position For Less Than 12 Months, Fair Value	14,166	27,952
In Unrealized Loss Position For Less Than 12 Months, Gross Unrealized Losses	6	30
In Unrealized Loss Position For Greater Than 12 Months, Fair Value	0	4,671
In Unrealized Loss Position For Greater Than 12 Months, Gross Unrealized Losses	$ 0	$ 10