Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Warrants	Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance (in shares) at Dec. 31, 2018		189,383,924
Balance at Dec. 31, 2018	$ 342,912	$ 1,942	$ 1,740,061	$ 13,063	$ 68	$ (1,412,222)
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net (in shares)		578,451
Stock issued from exercise of stock options, net	3,953	$ 6	3,947
Restricted stock tax vesting (in shares)		301,058
Restricted stock tax vesting	(1,940)		(1,940)
Stock issued for contingent consideration (in shares)		771,804
Stock issued for contingent consideration	9,316	$ 8	9,308
Stock-based compensation	12,744		12,744
Warrants exercised (in shares)		101,787
Warrants exercised	812	$ 1	1,487	(676)
Equity component of the convertible notes (in shares)		39,043,690
Equity component of the convertible notes	190,758	$ 390	190,368
Termination of capped call confirmations	14,632		14,632
Unrealized holding gain (loss) on available-for-sale securities	584				584
Foreign currency translation adjustment	(1,804)				(1,804)
Net loss	(120,299)					(120,299)
Balance (in shares) at Mar. 31, 2019		230,180,714
Balance at Mar. 31, 2019	$ 451,668	$ 2,347	1,970,607	12,387	(1,152)	(1,532,521)
Balance (in shares) at Dec. 31, 2019	255,417,869	255,417,869
Balance at Dec. 31, 2019	$ 476,425	$ 2,598	2,227,225	12,387	2,825	(1,768,610)
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net (in shares)		958,947
Stock issued from exercise of stock options, net	6,077	$ 9	6,068
Restricted stock tax vesting (in shares)		1,073,139
Restricted stock tax vesting	(7,543)		(7,543)
Stock-based compensation	12,596		12,596
Unrealized holding gain (loss) on available-for-sale securities	(209)				(209)
Foreign currency translation adjustment	4,196				4,196
Net loss	$ (88,948)					(88,948)
Balance (in shares) at Mar. 31, 2020	257,449,955	257,449,955
Balance at Mar. 31, 2020	$ 402,594	$ 2,607	$ 2,238,346	$ 12,387	$ 6,812	$ (1,857,558)