Financial Instruments - Schedule of Assets, Liabilities, and Equity Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Measurements, Recurring
Assets
Cash equivalents	$ 501,432	$ 892,361
Short-term investments	28,578	131,561
Loans held for sale	42,762	42,539
Other current assets	1,698	1,815
Long-term investments	53,488	11,922
Total assets	627,958	1,080,198
Liabilities
Total liabilities	149	517
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents	501,432	892,361
Loans held for sale	0	0
Other current assets	0	0
Total assets	583,498	1,035,844
Liabilities
Total liabilities	0	0
Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Cash equivalents	0	0
Loans held for sale	42,762	42,539
Other current assets	552	34
Total assets	43,314	42,573
Liabilities
Total liabilities	87	507
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	0	0
Loans held for sale	0	0
Other current assets	1,146	1,781
Total assets	1,146	1,781
Liabilities
Total liabilities	62	10
Fair Value, Measurements, Recurring \| Money market funds
Assets
Cash equivalents	501,432	886,261
Fair Value, Measurements, Recurring \| Money market funds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents	501,432	886,261
Fair Value, Measurements, Recurring \| Money market funds \| Significant Other Observable Inputs (Level 2)
Assets
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| Money market funds \| Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	0	0
Fair Value, Measurements, Recurring \| U.S. treasury securities
Assets
Cash equivalents		6,100
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents		6,100
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Significant Other Observable Inputs (Level 2)
Assets
Cash equivalents		0
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents		0
U.S. treasury securities \| Fair Value, Measurements, Recurring
Assets
Short-term investments	11,981	131,561
Long-term investments	53,488	0
U.S. treasury securities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	11,981	131,561
Long-term investments	53,488
U.S. treasury securities \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0	0
Long-term investments	0
U.S. treasury securities \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0	0
Long-term investments	0
Agency bonds \| Fair Value, Measurements, Recurring
Assets
Short-term investments	11,912	0
Long-term investments	0	11,922
Agency bonds \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	11,912
Long-term investments		11,922
Agency bonds \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0
Long-term investments		0
Agency bonds \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0
Long-term investments		0
Equity securities
Assets
Short-term investments	4,685
Long-term investments	0
Equity securities \| Fair Value, Measurements, Recurring
Assets
Short-term investments	4,685
Equity securities \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	4,685
Equity securities \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0
Equity securities \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0
Forward sales commitments \| Fair Value, Measurements, Recurring
Assets
Other current assets	552	34
Liabilities
Accrued liabilities	87	507
Forward sales commitments \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Other current assets	0	0
Liabilities
Accrued liabilities	0	0
Forward sales commitments \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Other current assets	552	34
Liabilities
Accrued liabilities	87	507
Forward sales commitments \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Other current assets	0	0
Liabilities
Accrued liabilities	0	0
IRLCs \| Fair Value, Measurements, Recurring
Assets
Other current assets	1,146	1,781
Liabilities
Accrued liabilities	62	10
IRLCs \| Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Other current assets	0	0
Liabilities
Accrued liabilities	0	0
IRLCs \| Fair Value, Measurements, Recurring \| Significant Other Observable Inputs (Level 2)
Assets
Other current assets	0	0
Liabilities
Accrued liabilities	0	0
IRLCs \| Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Other current assets	1,146	1,781
Liabilities
Accrued liabilities	$ 62	$ 10

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), classified as current.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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