CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Class A Common Stock Class A	Class A Common Stock Class A Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Class A Common Stock Class B Convertible	Class A Common Stock Class B Convertible Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Additional Paid-in Capital	Additional Paid-in Capital Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Treasury Stock	Treasury Stock Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment	Retained Earnings	Retained Earnings Cumulative Effect, Period of Adoption, Jan 1, 2021 Adjustment
Beginning Balance at Dec. 31, 2018	$ 529,731		$ 16		$ 2		$ 576,957		$ (586,161)		$ (10,217)		$ 549,134
Beginning Balance (in shares) at Dec. 31, 2018			15,837		2,035				(7,285)
Net (loss) income	34,355		$ 0		$ 0		0		$ 0		0		34,355
Other comprehensive income (loss)	566		0		0		0		0		566		0
Issuance of class A common stock under stock option plans	6,569		$ 0		$ 0		6,569		$ 0		0		0
Issuance of class A common stock under stock option plans (in shares)			51		0				0
Purchases of treasury stock	(72,719)		$ 0		$ 0		0		$ (72,719)		0		0
Purchases of treasury stock (in shares)			0		0				(522)
Share-based compensation expense	10,057		$ 0		$ 0		10,057		$ 0		0		0
Ending Balance at Dec. 31, 2019	508,559		$ 16		$ 2		593,583		$ (658,880)		(9,651)		583,489
Ending Balance (in shares) at Dec. 31, 2019			15,888		2,035				(7,807)
Net (loss) income	(7,524)		$ 0		$ 0		0		$ 0		0		(7,524)
Other comprehensive income (loss)	5,766		0		0		0		0		5,766		0
Conversion of class B to class A common stock	0		$ 0		$ 0		0		0		0		0
Conversion of class B to class A common stock (in shares)			71		(71)
Issuance of class A common stock under stock option plans	51,082		$ 0		$ 0		51,082		$ 0		0		0
Issuance of class A common stock under stock option plans (in shares)			348		0				0
Purchases of treasury stock	(123,224)		$ 0		$ 0		0		$ (123,224)		0		0
Purchases of treasury stock (in shares)			0		0				(877)
Share-based compensation expense	10,576		$ 0		$ 0		10,576		$ 0		0		0
Equity component of convertible senior notes, net of issuance cost and deferred tax liability	107,810		0		0		107,810		0		0		0
Ending Balance at Dec. 31, 2020	$ 553,045	$ (106,853)	$ 16	$ 0	$ 2	$ 0	763,051	$ (107,810)	$ (782,104)	$ 0	(3,885)	$ 0	575,965	$ 957
Ending Balance (in shares) at Dec. 31, 2020			16,307		1,964				(8,684)
Accounting Standards Update Description	ASU 2020-06
Net (loss) income	$ (535,480)		$ 0		$ 0		0		$ 0		0		(535,480)
Other comprehensive income (loss)	(3,658)		0		0		0		0		(3,658)		0
Issuance of class A common stock under stock option plans	40,651		$ 0		$ 0		40,651		$ 0		0		0
Issuance of class A common stock under stock option plans (in shares)			269		0				0
Issuance of class A common stock under employee stock purchase plans	2,854		$ 0		$ 0		2,854		$ 0		0		0
Issuance of class A common stock under employee stock purchase plans, (in shares)			5		0				0
Issuance of class A common stock upon vesting of restricted stock units, net of withholding taxes	(4,754)		$ 0		$ 0		(4,754)		$ 0		0		0
Issuance of class A common stock upon vesting of restricted stock units, net of withholding taxes, (in shares)			11		0				0
Issuance of class A common stock under public offerings, net of issuance costs	990,463		$ 2		$ 0		990,461		$ 0		0		0
Issuance of class A common stock under public offerings, net of issuance costs, (in shares)			1,414		0				0
Share-based compensation expense	42,690		$ 0		$ 0		42,690		$ 0		0		0
Ending Balance at Dec. 31, 2021	$ 978,958		$ 18		$ 2		$ 1,727,143		$ (782,104)		$ (7,543)		$ 41,442
Ending Balance (in shares) at Dec. 31, 2021			18,006		1,964				(8,684)