CONDENSED CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) $ in Thousands		Total		Common Stock	Additional Paid-in Capital	Company Stock Held By NQDC	Accumulated other comprehensive income (loss)	Accumulated Deficit
Beginning balance (in shares) at Dec. 31, 2017	[1]			175,844,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				1,664,000
Ending balance (in shares) at Jun. 30, 2018				177,508,000
Beginning Balance at Dec. 31, 2017	[1]	$ 2,808,663		$ 176	$ 4,483,220	$ (14,224)	$ (22,961)	$ (1,637,548)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				2	16,310
Stock-based compensation					77,770
Common stock held by the NQDC						834
Accounting impact of NQDC Plan change					0	0
Other comprehensive income (loss)							22,418
Net loss		(60,941)						(60,941)
Ending Balance at Jun. 30, 2018		2,885,104		$ 178	4,577,300	(13,390)	(1,129)	(1,677,855)
Beginning balance (in shares) at Mar. 31, 2018	[1]			176,653,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				855,000
Ending balance (in shares) at Jun. 30, 2018				177,508,000
Beginning Balance at Mar. 31, 2018	[1]	2,808,663		$ 177	4,510,451	(14,017)	(28,545)	(1,661,063)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				1	26,076
Stock-based compensation					40,773
Common stock held by the NQDC					0	627
Accounting impact of NQDC Plan change					0	0
Other comprehensive income (loss)							27,416
Net loss		(16,792)						(16,792)
Ending Balance at Jun. 30, 2018		2,885,104		$ 178	4,577,300	(13,390)	(1,129)	(1,677,855)
Beginning balance (in shares) at Dec. 31, 2018	[1]			178,253,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				1,180,000
Ending balance (in shares) at Jun. 30, 2019				179,433,000
Beginning Balance at Dec. 31, 2018	[1]	2,967,940	[2]	$ 178	4,669,926	(13,301)	5,271	(1,694,134)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				1	(17,889)
Stock-based compensation					82,068
Common stock held by the NQDC					(442)	442
Accounting impact of NQDC Plan change					10,653	2,648
Other comprehensive income (loss)							12,168
Net loss		(93,908)						(93,908)
Ending Balance at Jun. 30, 2019		2,960,954		$ 179	4,744,316	(10,211)	17,439	(1,790,769)
Beginning balance (in shares) at Mar. 31, 2019	[1]			179,033,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans (in shares)				400,000
Ending balance (in shares) at Jun. 30, 2019				179,433,000
Beginning Balance at Mar. 31, 2019	[1]	2,967,940		$ 179	4,682,900	(12,912)	19,794	(1,753,334)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuances under equity incentive plans, net of tax				0	10,843
Stock-based compensation					40,362
Common stock held by the NQDC					(442)	53
Accounting impact of NQDC Plan change					10,653	2,648
Other comprehensive income (loss)							(2,355)
Net loss		(37,435)						(37,435)
Ending Balance at Jun. 30, 2019		$ 2,960,954		$ 179	$ 4,744,316	$ (10,211)	$ 17,439	$ (1,790,769)

[1] The beginning balances for the six month periods were derived from the audited Consolidated Financial Statements included in Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on February 28, 2019.

[2] December 31, 2018 balances were derived from the audited Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018, filed with the SEC on February 28, 2019.