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Debt - Narrative (Details) $ / shares in Units, $ in Thousands			3 Months Ended			9 Months Ended
	Mar. 25, 2021 USD ($) $ / shares shares	Jan. 12, 2021	Sep. 30, 2021 USD ($) shares	Mar. 31, 2021	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) tradingDay businessDay	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Oct. 20, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 23, 2018 USD ($)
Debt Instrument [Line Items]
Inventory			$ 435,144			$ 435,144		$ 49,158
Cash, cash equivalents, restricted cash and restricted cash equivalents			637,246		$ 387,966	637,246	$ 387,966	945,820		$ 247,448
Proceeds from issuance of convertible senior notes, net of issuance costs						561,529	0
Adjustments to additional paid in capital, convertible debt, capped call transaction			62,647			$ 62,647
Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Conversion price, percentage						98.00%
1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Aggregated principal amount			23,512			$ 23,512
Debt conversion						226
Converted instrument			$ 234
Common stock (in shares) \| shares			3,164
0% Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Aggregated principal amount			$ 661,250			661,250
0.5% Convertible Senior Notes Due 2027
Debt Instrument [Line Items]
Aggregated principal amount			575,000			575,000
Revolving Credit Facility
Debt Instrument [Line Items]
Net assets			511,569			511,569		65,191
Inventory			415,610			415,610		47,620
Cash, cash equivalents, restricted cash and restricted cash equivalents			25,446			25,446		11,818
Amortization of debt issuance costs			81		155	217	464
Interest expense, debt			$ 1,375		101	$ 2,328	432
Western Alliance Bank \| Warehouse Agreement Borrowings
Debt Instrument [Line Items]
Stated Cash Interest Rate			3.25%			3.25%
Western Alliance Bank \| Warehouse Agreement Borrowings \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate						2.00%
Texas Capital Bank, N.A. \| Warehouse Agreement Borrowings
Debt Instrument [Line Items]
Stated Cash Interest Rate			2.95%			2.95%
Decrease in rate of interest accruing on outstanding principal						0.25%
Flagstar Bank, FSB \| Warehouse Agreement Borrowings
Debt Instrument [Line Items]
Stated Cash Interest Rate			3.00%			3.00%
Facility termination period						30 days
Flagstar Bank, FSB \| Warehouse Agreement Borrowings \| London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate						2.00%
Goldman Sachs Bank USA \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, term						6 months
Minimum \| Goldman Sachs Bank USA \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, floor rate of basis spread on variable rate		0.50%		0.30%
Maximum \| Goldman Sachs Bank USA \| Revolving Credit Facility
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate				3.00%
Senior Notes
Debt Instrument [Line Items]
Amortization of debt issuance costs			$ 1,291		189	$ 3,366	562
Interest expense, debt			$ 822		629	$ 1,779	1,887
Senior Notes \| 1.75% Convertible Senior Notes due 2023
Debt Instrument [Line Items]
Stated Cash Interest Rate			1.75%			1.75%
Amortization of debt issuance costs			$ 41		189	$ 151	562
Interest expense, debt			103		629	311	1,887
Aggregated principal amount			23,512			23,512		25,626			$ 143,750
Repurchased face amount			120,238			120,238
Senior Notes \| 0% Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Amortization of debt issuance costs			690		0	2,070	0
Interest expense, debt			0		0	0	0
Aggregated principal amount			$ 661,250			$ 661,250		$ 661,250	$ 661,250
Senior Notes \| 0.5% Convertible Senior Notes Due 2027
Debt Instrument [Line Items]
Stated Cash Interest Rate			0.50%			0.50%
Amortization of debt issuance costs			$ 560		0	$ 1,145	0
Interest expense, debt			719		$ 0	1,468	$ 0
Aggregated principal amount	$ 575,000		$ 575,000			$ 575,000
Proceeds from issuance of convertible senior notes, net of issuance costs	$ 561,529
Common stock covered under capped calls (in shares) \| shares	6,147,900
Senior Notes \| Convertible Senior Notes \| Debt Instrument, Redemption, Period One
Debt Instrument [Line Items]
Threshold trading days \| tradingDay						20
Threshold consecutive trading days \| tradingDay						30
Threshold percentage of stock price trigger						130.00%
Senior Notes \| Convertible Senior Notes \| Debt Instrument, Redemption, Period Two
Debt Instrument [Line Items]
Threshold trading days \| businessDay						5
Threshold consecutive trading days \| tradingDay						5
Senior Notes \| Minimum \| 0.5% Convertible Senior Notes Due 2027 \| Call Option \| Capped Call Transaction
Debt Instrument [Line Items]
Capped call price (in dollars per share) \| $ / shares	$ 93.53
Senior Notes \| Maximum \| 0.5% Convertible Senior Notes Due 2027 \| Call Option \| Capped Call Transaction
Debt Instrument [Line Items]
Capped call price (in dollars per share) \| $ / shares	$ 138.56