Marketable Securities - Summary of Marketable Securities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	$ 53,238	$ 91,359
Unrealized Gains	1,151	411
Unrealized Losses	(5)	(1,180)
Fair Value	54,384	90,590
Equity securities
Debt Securities, Trading, and Equity Securities, FV-NI [Abstract]
Adjusted Cost	4,234	10,101
Unrealized Gains	170	0
Unrealized Losses	0	(956)
Fair Value	4,404	9,145
Money market funds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	38,028	52,733
Unrealized Gains	771	316
Unrealized Losses	0	(53)
Fair Value	38,799	52,996
Corporate bonds
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	4,021	6,411
Unrealized Gains	77	7
Unrealized Losses	0	(79)
Fair Value	4,098	6,339
Government securities - U.S.
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	5,341	12,714
Unrealized Gains	110	66
Unrealized Losses	(5)	(79)
Fair Value	5,446	12,701
Other fixed-income securities
Debt Securities, Available-for-sale, Fair Value to Amortized Cost [Abstract]
Adjusted Cost	1,614	9,400
Unrealized Gains	23	22
Unrealized Losses	0	(13)
Fair Value	$ 1,637	$ 9,409

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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