Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Mar. 31, 2020
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	$ 53,238	$ 39,639
Unrealized Gains	1,151	758
Unrealized Losses	(5)	(420)
Fair Value	54,384	39,977
Equity securities
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Adjusted Cost	4,234
Unrealized Gains	170
Unrealized Losses	0
Fair Value	4,404
Money market and mutual funds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	38,028	28,370
Unrealized Gains	771	410
Unrealized Losses	0	(308)
Fair Value	38,799	28,472
Corporate bonds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	4,021	4,074
Unrealized Gains	77	33
Unrealized Losses	0	(94)
Fair Value	4,098	4,013
Government securities - U.S.
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	5,341	5,777
Unrealized Gains	110	308
Unrealized Losses	(5)	0
Fair Value	5,446	6,085
Other fixed-income securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	1,614	1,418
Unrealized Gains	23	7
Unrealized Losses	0	(18)
Fair Value	$ 1,637	$ 1,407

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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