Fair Value Measurements - Contingent Consideration (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Dec. 31, 2019	[1]
Fair Value Measurements
Changes in estimated fair value of contingent consideration	$ 0
Contingent consideration under royalty purchase agreements	$ 75	$ 75

[1] The consolidated balance sheet as of December 31, 2019 has been derived from the audited consolidated financial statements as of that date included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2019.