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Debt - Narrative (Details) $ / shares in Units, $ in Thousands				1 Months Ended	3 Months Ended			6 Months Ended
	Apr. 05, 2021 USD ($) shares	Mar. 25, 2021 USD ($) $ / shares shares	Jan. 12, 2021	Aug. 05, 2021 USD ($)	Jun. 30, 2021 USD ($) shares	Mar. 31, 2021	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) tradingDay businessDay	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Oct. 20, 2020 USD ($)	Dec. 31, 2019 USD ($)	Jul. 23, 2018 USD ($)
Debt Instrument [Line Items]
Inventory					$ 249,003			$ 249,003		$ 49,158
Cash, cash equivalents, restricted cash and restricted cash equivalents					787,682		$ 360,454	787,682	$ 360,454	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					54,450			$ 54,450
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					23,738			$ 23,738
Debt conversion								39
Converted instrument					$ 39
Common stock (in shares) \| shares					624
1.75% Convertible Senior Notes due 2023 \| Subsequent Event
Debt Instrument [Line Items]
Debt conversion				$ 226
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					329,224			329,224		65,191
Inventory					240,357			240,357		47,620
Cash, cash equivalents, restricted cash and restricted cash equivalents					48,177			48,177		11,818
Amortization of debt issuance costs					50		155	136	309
Interest expense, debt					$ 613		251	$ 953	331
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					3.35%			3.35%
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					$ 1,286		187	$ 2,075	373
Interest expense, debt					$ 819		629	$ 957	1,258
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					$ 39		187	$ 110	373
Interest expense, debt					104		629	208	1,258
Aggregated principal amount					23,738			23,738		25,626			$ 143,750
Repurchased face amount					120,012			120,012
Senior Notes \| 0% Convertible Senior Notes due 2025
Debt Instrument [Line Items]
Amortization of debt issuance costs					690		0	1,380	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					$ 557		0	$ 585	0
Interest expense, debt					715		$ 0	749	$ 0
Aggregated principal amount	$ 75,000	$ 500,000			$ 575,000			$ 575,000
Proceeds from issuance of convertible senior notes, net of issuance costs	$ 73,296	$ 488,234
Common stock covered under capped calls (in shares) \| shares	801,900	5,346,000
Adjustments to additional paid in capital, convertible debt, capped call transaction	$ 8,168
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