Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock and Additional Paid-in-Capital	Treasury Stock	Accumulated Other Comprehensive Income (Loss)	Accumulated Deficit
Beginning balance at Dec. 31, 2018	$ 650,394	$ 3,152,179	$ (150,000)	$ (2,299)	$ (2,349,486)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings		1,494
Shares withheld for taxes		0
Issuance of common stock related to employee stock purchase plan		12,315
Shares retired		0	0
Issuance of common stock and assumption of options related to Verodin, Inc. acquisition		121,158
Stock-based compensation		82,838
Unrealized gain investments, net of tax				3,269
Net loss	(142,698)
Ending balance at Jun. 30, 2019	728,770	3,369,984	(150,000)	970	(2,492,184)
Beginning balance at Mar. 31, 2019	619,441	3,194,504	(150,000)	(202)	(2,424,861)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings		651
Shares withheld for taxes		0
Issuance of common stock related to employee stock purchase plan		12,315
Shares retired		0	0
Issuance of common stock and assumption of options related to Verodin, Inc. acquisition		121,158
Stock-based compensation		41,356
Unrealized gain investments, net of tax				1,172
Net loss	(67,323)
Ending balance at Jun. 30, 2019	728,770	3,369,984	(150,000)	970	(2,492,184)
Beginning balance at Dec. 31, 2019	701,666	3,457,381	(150,000)	1,180	(2,606,895)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings		3,731
Shares withheld for taxes		(8,039)
Issuance of common stock related to employee stock purchase plan		12,300
Shares retired		(70,000)	(70,000)
Issuance of common stock and assumption of options related to Verodin, Inc. acquisition
Stock-based compensation		75,152
Unrealized gain investments, net of tax				5,131
Net loss	(129,582)				(129,582)
Ending balance at Jun. 30, 2020	660,359	3,470,525	(80,000)	6,311	(2,736,477)
Beginning balance at Mar. 31, 2020	653,608	3,488,478	(150,000)	(1,669)	(2,683,201)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of common stock for equity awards, net of tax withholdings		2,383
Shares withheld for taxes		(640)
Issuance of common stock related to employee stock purchase plan		12,300
Shares retired		(70,000)	(70,000)
Issuance of common stock and assumption of options related to Verodin, Inc. acquisition		0
Stock-based compensation		38,004
Unrealized gain investments, net of tax				7,980
Net loss	(53,276)
Ending balance at Jun. 30, 2020	$ 660,359	$ 3,470,525	$ (80,000)	$ 6,311	$ (2,736,477)