CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net loss before noncontrolling interest	$ (14,000)	$ (10,976)	$ (26,186)	$ (21,790)
Other comprehensive income (loss):
Foreign currency translation adjustments	0	(424)	0	238
Other Comprehensive Income (Loss), Foreign Currency Transaction And Translation Adjustment, Intercompany Balance, Net Of Tax	0	428	0	(251)
Net unrealized gain on available-for-sale securities	0	8	0	34
Other comprehensive income	0	12	0	21
Comprehensive loss	(14,000)	(10,964)	(26,186)	(21,769)
Comprehensive loss attributable to noncontrolling interest	0	5	0	5
Comprehensive loss attributable to CTI	$ (14,000)	$ (10,959)	$ (26,186)	$ (21,764)