CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income
Balance at period start (in shares) at Dec. 31, 2018			46,984
Balance at period start at Dec. 31, 2018		$ 512,329	$ 470	$ 617,937	$ (108,751)	$ 2,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for business combination (in shares)			2,364
Issuance of common stock for business combination		36,980	$ 23	36,957
Stock-based compensation (in shares)			246
Stock-based compensation		1,535	$ 3	1,532
Purchase of common stock for retirement (in shares)			(44)
Purchase of common stock for retirement		(734)		(734)
Net loss		61,092			61,092
Balance at period end (in shares) at Mar. 31, 2019			49,550
Balance at period end at Mar. 31, 2019		611,202	$ 496	655,692	(47,659)	2,673
Balance at period start (in shares) at Dec. 31, 2018			46,984
Balance at period start at Dec. 31, 2018		512,329	$ 470	617,937	(108,751)	2,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss		5,370
Balance at period end (in shares) at Sep. 30, 2019			51,168
Balance at period end at Sep. 30, 2019		579,510	$ 512	679,706	(103,381)	2,673
Balance at period start (in shares) at Mar. 31, 2019			49,550
Balance at period start at Mar. 31, 2019		611,202	$ 496	655,692	(47,659)	2,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for convertible notes repurchase, net (in shares)	[1]		1,449
Issuance of common stock for convertible notes repurchase, net	[1]	17,789	$ 14	17,775
Issuance of common stock for employee stock purchase plan (in shares)			37
Issuance of common stock for employee stock purchase plan		754		754
Stock-based compensation (in shares)			(31)
Stock-based compensation		1,550		1,550
Purchase of common stock for retirement (in shares)			(2)
Purchase of common stock for retirement		(20)		(20)
Exercise of stock options (in shares)			21
Exercise of stock options		119		119
Net loss		28,169			28,169
Balance at period end (in shares) at Jun. 30, 2019			51,024
Balance at period end at Jun. 30, 2019		659,563	$ 510	675,870	(19,490)	2,673
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)			(20)
Stock-based compensation		1,448		1,448
Purchase of common stock for retirement (in shares)			(6)
Purchase of common stock for retirement		(414)		(414)
Exercise of stock options (in shares)			170
Exercise of stock options		2,804	$ 2	2,802
Net loss		(83,891)			(83,891)
Balance at period end (in shares) at Sep. 30, 2019			51,168
Balance at period end at Sep. 30, 2019		579,510	$ 512	679,706	(103,381)	2,673
Balance at period start (in shares) at Dec. 31, 2019			53,254
Balance at period start at Dec. 31, 2019		648,242	$ 533	715,069	(67,942)	582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)			296
Stock-based compensation		1,615	$ 3	1,612
Purchase of common stock for retirement (in shares)			(64)
Purchase of common stock for retirement		(1,068)	$ (1)	(1,067)
Exercise of stock options (in shares)			351
Exercise of stock options		3,936	$ 3	3,933
Net loss		(222,337)			(222,337)
Balance at period end (in shares) at Mar. 31, 2020			53,837
Balance at period end at Mar. 31, 2020		430,388	$ 538	719,547	(290,279)	582
Balance at period start (in shares) at Dec. 31, 2019			53,254
Balance at period start at Dec. 31, 2019		648,242	$ 533	715,069	(67,942)	582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net loss		(277,168)
Balance at period end (in shares) at Sep. 30, 2020			53,947
Balance at period end at Sep. 30, 2020		379,940	$ 539	723,929	(345,110)	582
Balance at period start (in shares) at Mar. 31, 2020			53,837
Balance at period start at Mar. 31, 2020		430,388	$ 538	719,547	(290,279)	582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for employee stock purchase plan (in shares)			95
Issuance of common stock for employee stock purchase plan		855	$ 1	854
Stock-based compensation (in shares)			10
Stock-based compensation		1,794		1,794
Purchase of common stock for retirement		(1)		(1)
Net loss		(40,560)			(40,560)
Balance at period end (in shares) at Jun. 30, 2020			53,942
Balance at period end at Jun. 30, 2020		392,476	$ 539	722,194	(330,839)	582
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation (in shares)			10
Stock-based compensation		1,777	$ 0	1,777	0	0
Purchase of common stock for retirement (in shares)			(5)
Purchase of common stock for retirement		(42)	$ 0	(42)
Net loss		(14,271)			(14,271)
Balance at period end (in shares) at Sep. 30, 2020			53,947
Balance at period end at Sep. 30, 2020		$ 379,940	$ 539	$ 723,929	$ (345,110)	$ 582

[1] The issuance of common stock for the repurchase of a portion of our 5.00% Convertible Senior Notes in the three months ended June 30, 2019 is presented net of a $12.3 million write-off associated with the equity component of the repurchased notes.