Revenue Recognition - Components of Accounts Receivable (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue from Contract with Customer [Abstract]
Trade receivables	$ 6,425	$ 14,261
Unbilled receivables	1,857	5,540
Other short-term receivables	7	9
Allowance for doubtful accounts	(1,816)	(1,411)	$ (1,545)	$ (1,569)
Total accounts receivable	$ 6,473	$ 18,399