Financial Instruments - Schedule of Assets, Liabilities, and Equity Measured at Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Equity securities
Assets
Short-term investments	$ 5,113
Fair Value, Measurements, Recurring
Assets
Cash equivalents	509,971	$ 892,361
Short-term investments	33,737	131,561
Loans held for sale	35,759	42,539
Prepaid expenses and other current assets	1,329	1,815
U.S. treasury securities	54,828	11,922
Total assets	635,624	1,080,198
Liabilities
Total liabilities	153	517
Fair Value, Measurements, Recurring \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents	509,971	892,361
Loans held for sale	0	0
Prepaid expenses and other current assets	0	0
Total assets	598,536	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	35,759	42,539
Prepaid expenses and other current assets	138	34
Total assets	35,897	42,573
Liabilities
Total liabilities	93	507
Fair Value, Measurements, Recurring \| Significant Unobservable Inputs (Level 3)
Assets
Cash equivalents	0	0
Loans held for sale	0	0
Prepaid expenses and other current assets	1,191	1,781
Total assets	1,191	1,781
Liabilities
Total liabilities	60	10
Fair Value, Measurements, Recurring \| U.S. treasury securities
Assets
Short-term investments	16,718	131,561
U.S. treasury securities	54,828	0
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	16,718	131,561
U.S. treasury securities	54,828
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0	0
U.S. treasury securities	0
Fair Value, Measurements, Recurring \| U.S. treasury securities \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0	0
U.S. treasury securities	0
Fair Value, Measurements, Recurring \| Agency bonds
Assets
Short-term investments	11,906	0
U.S. treasury securities	0	11,922
Fair Value, Measurements, Recurring \| Agency bonds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	11,906
U.S. treasury securities		11,922
Fair Value, Measurements, Recurring \| Agency bonds \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0
U.S. treasury securities		0
Fair Value, Measurements, Recurring \| Agency bonds \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0
U.S. treasury securities		0
Fair Value, Measurements, Recurring \| Equity securities
Assets
Short-term investments	5,113
U.S. treasury securities	0
Fair Value, Measurements, Recurring \| Equity securities \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Short-term investments	5,113
Fair Value, Measurements, Recurring \| Equity securities \| Significant Other Observable Inputs (Level 2)
Assets
Short-term investments	0
Fair Value, Measurements, Recurring \| Equity securities \| Significant Unobservable Inputs (Level 3)
Assets
Short-term investments	0
Fair Value, Measurements, Recurring \| Forward sales commitments
Assets
Prepaid expenses and other current assets	138	34
Liabilities
Liabilities	93	507
Fair Value, Measurements, Recurring \| Forward sales commitments \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Prepaid expenses and other current assets	0	0
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring \| Forward sales commitments \| Significant Other Observable Inputs (Level 2)
Assets
Prepaid expenses and other current assets	138	34
Liabilities
Liabilities	93	507
Fair Value, Measurements, Recurring \| Forward sales commitments \| Significant Unobservable Inputs (Level 3)
Assets
Prepaid expenses and other current assets	0	0
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring \| IRLCs
Assets
Prepaid expenses and other current assets	1,191	1,781
Liabilities
Liabilities	60	10
Fair Value, Measurements, Recurring \| IRLCs \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Prepaid expenses and other current assets	0	0
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring \| IRLCs \| Significant Other Observable Inputs (Level 2)
Assets
Prepaid expenses and other current assets	0	0
Liabilities
Liabilities	0	0
Fair Value, Measurements, Recurring \| IRLCs \| Significant Unobservable Inputs (Level 3)
Assets
Prepaid expenses and other current assets	1,191	1,781
Liabilities
Liabilities	60	10
Fair Value, Measurements, Recurring \| Money market funds
Assets
Cash equivalents	509,971	886,261
Fair Value, Measurements, Recurring \| Money market funds \| Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets
Cash equivalents	509,971	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

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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 portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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