Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	At-the-market Offering [Member] Common Stock [Member]	At-the-market Offering [Member] Common Stock Subscribed [Member]	At-the-market Offering [Member] Additional Paid-in Capital [Member]	At-the-market Offering [Member] Retained Earnings [Member]	At-the-market Offering [Member] AOCI Attributable to Parent [Member]	At-the-market Offering [Member] Subscription Receivable [Member]	At-the-market Offering [Member] Treasury Stock [Member]	At-the-market Offering [Member]	Public Offering [Member] Common Stock [Member]	Public Offering [Member] Common Stock Subscribed [Member]	Public Offering [Member] Additional Paid-in Capital [Member]	Public Offering [Member] Retained Earnings [Member]	Public Offering [Member] AOCI Attributable to Parent [Member]	Public Offering [Member] Subscription Receivable [Member]	Public Offering [Member] Treasury Stock [Member]	Public Offering [Member]	Common Stock [Member]	Common Stock Subscribed [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Subscription Receivable [Member]	Treasury Stock [Member]	Total
Balance (in shares) at Dec. 31, 2016																	70,390						(200)
Balance at Dec. 31, 2016																	$ 92		$ 598,069	$ (490,573)	$ (85)		$ (2,741)	$ 104,762
Net loss																				(51,013)				(51,013)
Foreign currency translation adjustment																					52			52
Return of purchase premium for noncontrolling interests																			15					15
Stock-based compensation expense																			4,142					4,142
Exercise of stock options (in shares)																	80
Exercise of stock options																			469					469
Issuance of common stock (in shares)	855
Issuance of common stock	$ 1		$ 5,025					$ 5,026
Subscription of common stock in connection with at-the-market offering, net of commissions (in shares)		320
Subscription of common stock in connection with at-the-market offering, net of commissions			2,109			(2,109)
Balance (in shares) at Dec. 31, 2017																	71,325	320					(200)
Balance at Dec. 31, 2017																	$ 93		609,829	(541,586)	(33)	(2,109)	$ (2,741)	63,453
Net loss																				(67,657)				(67,657)
Foreign currency translation adjustment																					(72)			(72)
Stock-based compensation expense																			5,209					5,209
Exercise of stock options (in shares)																	96
Exercise of stock options																			467					467
Issuance of common stock (in shares)	4,230	(320)						3,900	9,091							9,100
Issuance of common stock	$ 5		$ 27,539			$ 2,109		$ 29,653	$ 12		$ 69,975					$ 69,987
Cumulative effect of ASU 2014-09 adoption																				35				35
Balance (in shares) at Dec. 31, 2018																	84,742						(200)
Balance at Dec. 31, 2018																	$ 110		713,019	(609,208)	(105)		$ (2,741)	101,075
Net loss																				(68,552)				(68,552)
Foreign currency translation adjustment																					(43)			(43)
Stock-based compensation expense																			4,392					$ 4,392
Exercise of stock options (in shares)																	386							386
Exercise of stock options																	$ 1		1,941					$ 1,942
Issuance of common stock to MIP Shareholders (in shares)																	1,632
Issuance of common stock to MIP Shareholders																	$ 2		7,737					7,739
Balance (in shares) at Dec. 31, 2019																	86,760						(200)
Balance at Dec. 31, 2019																	$ 113		$ 727,089	$ (677,760)	$ (148)		$ (2,741)	$ 46,553