Fair Value Measurements - Changes in Fair Value of Liabilities-Classified as Stock Option (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 479
Liability at end of the period	253	$ 479
Liability classified stock options
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	479	1,239
Fair value of liability-classified options exercised in the period	0	93
Increase (decrease) in fair value of liability	(226)	(667)
Liability at end of the period	$ 253	$ 479