Fair Value Measurement - Assets and Liabilities on Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Liabilities
Contingent consideration, fair value	$ 7,100	$ 16,975	$ 8,100	$ 8,800
Warrants and rights outstanding (in shares)	1,513,786	1,513,786
Fair Value, Recurring
Assets
Cash and cash equivalents	$ 2,824	$ 3,698
Restricted cash and restricted investments	1,006	1,004
Total fair value of assets measured on a recurring basis	3,830	4,702
Liabilities
Contingent consideration, liability	4,000	9,883
Warrants	3,100	7,092
Total fair value of liabilities measured on a recurring basis	7,100	16,975
Level 1 | Fair Value, Recurring
Assets
Cash and cash equivalents	2,824	3,698
Restricted cash and restricted investments	1,006	1,004
Total fair value of assets measured on a recurring basis	3,830	4,702
Liabilities
Contingent consideration, liability	0	0
Warrants	0	0
Total fair value of liabilities measured on a recurring basis	0	0
Level 2 | Fair Value, Recurring
Assets
Cash and cash equivalents	0	0
Restricted cash and restricted investments	0	0
Total fair value of assets measured on a recurring basis	0	0
Liabilities
Contingent consideration, liability	0	0
Warrants	0	0
Total fair value of liabilities measured on a recurring basis	0	0
Level 3 | Fair Value, Recurring
Assets
Cash and cash equivalents	0	0
Restricted cash and restricted investments	0	0
Total fair value of assets measured on a recurring basis	0	0
Liabilities
Contingent consideration, liability	4,000	9,883
Warrants	3,100	7,092
Total fair value of liabilities measured on a recurring basis	7,100	16,975
Black-Scholes | Warrant | Level 3 | Fair Value, Recurring
Liabilities
Warrants	$ 3,100	$ 7,092