Cash and Marketable Securities - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Other-than-temporary impairment	$ 0	$ 0
Income tax benefit	$ 351	0	$ 0
Effective maturity (less than)	2 years
Unrealized gains in other comprehensive income	$ (400)	$ 0	$ 0