Fair Value of Financial Instruments - Changes in Fair Value of Liabilities-Classified as Stock Option (Details) - Liability classified stock options - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 253	$ 479
Fair value of liability-classified options exercised in the period	(9)	0
Increase (decrease) in fair value of liability	(186)	(65)
Liability at end of the period	$ 58	$ 414