CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) - USD ($)	Common Stock	Additional Paid-In Capital	Accumulated Deficit	Accumulated Other Comprehensive Income	Total
Balance as of beginning of the period at Dec. 31, 2018	$ 70,000	$ 1,434,780,000	$ (408,661,000)	$ (13,070,000)	$ 1,013,119,000
Balance as of beginning of the period (in shares) at Dec. 31, 2018	70,516,249
Stockholders' Equity (Deficit)
Exercise of stock options	$ 1,000	8,853,000	0	0	8,854,000
Exercise of stock options (in shares)	564,102
Issuance of common stock upon vesting of restricted stock units	$ 0	0	0	0	0
Issuance of common stock upon vesting of restricted stock units (in shares)	383,060
Stock-based compensation	$ 0	13,523,000	0	0	13,523,000
Other comprehensive income (loss), net of tax	0	0	0	(3,788,000)	(3,788,000)
Net loss	0	0	(30,150,000)	0	(30,150,000)
Balance as of end of the period at Mar. 31, 2019	$ 71,000	1,457,156,000	(438,811,000)	(16,858,000)	1,001,558,000
Balance as of end of the period (in shares) at Mar. 31, 2019	71,463,411
Balance as of beginning of the period at Dec. 31, 2018	$ 70,000	1,434,780,000	(408,661,000)	(13,070,000)	1,013,119,000
Balance as of beginning of the period (in shares) at Dec. 31, 2018	70,516,249
Stockholders' Equity (Deficit)
Net loss					(59,474,000)
Balance as of end of the period at Jun. 30, 2019	$ 72,000	1,483,245,000	(468,135,000)	(12,542,000)	1,002,640,000
Balance as of end of the period (in shares) at Jun. 30, 2019	71,934,381
Balance as of beginning of the period at Mar. 31, 2019	$ 71,000	1,457,156,000	(438,811,000)	(16,858,000)	1,001,558,000
Balance as of beginning of the period (in shares) at Mar. 31, 2019	71,463,411
Stockholders' Equity (Deficit)
Exercise of stock options	$ 1,000	6,846,000	0	0	6,847,000
Exercise of stock options (in shares)	350,219
Issuance of common stock upon vesting of restricted stock units	$ 0	0	0	0	0
Issuance of common stock upon vesting of restricted stock units (in shares)	85,035
Issuance of stock under employee stock purchase plan	$ 0	1,875,000	0	0	1,875,000
Issuance of stock under employee stock purchase plan (in shares)	35,716
Stock-based compensation	$ 0	17,368,000	0	0	17,368,000
Other comprehensive income (loss), net of tax	0	0	0	4,316,000	4,316,000
Net loss	0	0	(29,324,000)	0	(29,324,000)
Balance as of end of the period at Jun. 30, 2019	$ 72,000	1,483,245,000	(468,135,000)	(12,542,000)	1,002,640,000
Balance as of end of the period (in shares) at Jun. 30, 2019	71,934,381
Balance as of beginning of the period at Dec. 31, 2019	$ 73,000	1,538,716,000	(507,525,000)	(17,239,000)	1,014,025,000
Balance as of beginning of the period (in shares) at Dec. 31, 2019	72,761,941
Stockholders' Equity (Deficit)
Exercise of stock options	$ 0	14,830,000	0	0	14,830,000
Exercise of stock options (in shares)	671,279
Issuance of common stock upon vesting of restricted stock units	$ 1,000	(1,000)	0	0	0
Issuance of common stock upon vesting of restricted stock units (in shares)	642,411
Issuance of common stock for 2022 Notes	$ 0	58,000	0	0	58,000
Issuance of common stock for 2022 Notes (in shares)	655
Stock-based compensation	$ 0	18,421,000	0	0	18,421,000
Other comprehensive income (loss), net of tax	0	0	0	(17,554,000)	(17,554,000)
Net loss	0	0	(29,603,000)	0	(29,603,000)
Balance as of end of the period at Mar. 31, 2020	$ 74,000	1,572,024,000	(537,128,000)	(34,793,000)	1,000,177,000
Balance as of end of the period (in shares) at Mar. 31, 2020	74,076,286
Balance as of beginning of the period at Dec. 31, 2019	$ 73,000	1,538,716,000	(507,525,000)	(17,239,000)	1,014,025,000
Balance as of beginning of the period (in shares) at Dec. 31, 2019	72,761,941
Stockholders' Equity (Deficit)
Net loss					(55,285,000)
Balance as of end of the period at Jun. 30, 2020	$ 79,000	1,879,573,000	(562,810,000)	(21,913,000)	1,294,929,000
Balance as of end of the period (in shares) at Jun. 30, 2020	79,099,433
Balance as of beginning of the period at Mar. 31, 2020	$ 74,000	1,572,024,000	(537,128,000)	(34,793,000)	1,000,177,000
Balance as of beginning of the period (in shares) at Mar. 31, 2020	74,076,286
Stockholders' Equity (Deficit)
Exercise of stock options	$ 1,000	18,682,000	0	0	18,683,000
Exercise of stock options (in shares)	927,684
Issuance of common stock upon vesting of restricted stock units	$ 0	0	0	0	0
Issuance of common stock upon vesting of restricted stock units (in shares)	109,768
Issuance of stock under employee stock purchase plan	$ 0	2,473,000	0	0	2,473,000
Issuance of stock under employee stock purchase plan (in shares)	35,901
Issuance of common stock for 2022 Notes	$ 4,000	693,802,000	0	0	693,806,000
Issuance of common stock for 2022 Notes (in shares)	3,949,794
Equity portion of extinguishment of 2022 Convertible Notes	$ 0	(715,151,000)	0	0	(715,151,000)
Equity component of 2027 Notes, net of issuance costs	0	285,601,000	0	0	285,601,000
Stock-based compensation	0	22,142,000	0	0	22,142,000
Other comprehensive income (loss), net of tax	0	0	0	12,880,000	12,880,000
Net loss	0	0	(25,682,000)	0	(25,682,000)
Balance as of end of the period at Jun. 30, 2020	$ 79,000	$ 1,879,573,000	$ (562,810,000)	$ (21,913,000)	$ 1,294,929,000
Balance as of end of the period (in shares) at Jun. 30, 2020	79,099,433