Borrowings - Narrative (Details) $ / shares in Units, $ in Thousands, shares in Millions		1 Months Ended		3 Months Ended
	Aug. 20, 2021 USD ($) day optionToExtend $ / shares	Dec. 31, 2021 USD ($)	Nov. 30, 2015 USD ($)	Mar. 31, 2022 USD ($) $ / shares shares	Sep. 30, 2019
Schedule of Borrowings [Line Items]
Outstanding borrowings		$ 709,787		$ 782,801
ULT Warehouse Credit Facility | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Maximum borrowing capacity			$ 100,000
Redemption price (in percent)			100.00%
Minimum utilization requirement			$ 30,000
Maximum advance rate (in percent)		85.00%		85.00%
ULT Warehouse Credit Facility | Minimum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Monthly unused fee (in percent)			0.10%
ULT Warehouse Credit Facility | Maximum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Monthly unused fee (in percent)			1.00%
UAWT Warehouse Credit Facility | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Maximum borrowing capacity		$ 100,000
Monthly unused fee (in percent)		0.50%
Maximum advance rate (in percent)		82.50%		82.50%
2019-2 RR Financing Agreement
Schedule of Borrowings [Line Items]
Outstanding borrowings		$ 500
Stated interest rate					4.33%
Assets pledged as collateral		4,800
2026 ("Notes")
Schedule of Borrowings [Line Items]
Outstanding borrowings		661,250		$ 661,250
Convertible notes payable		646,900		647,700
Purchase of capped calls				$ 58,500
Initial conversion price (in dollars per share) | $ / shares				$ 285.26
Initial cap price (in dollars per share) | $ / shares				$ 400.36
Capped call cover (in shares) | shares				2.3
2026 ("Notes") | Fair Value, Inputs, Level 2
Schedule of Borrowings [Line Items]
Fair value of convertible senior notes		$ 627,500		$ 564,200
2026 ("Notes") | Convertible Debt
Schedule of Borrowings [Line Items]
Stated interest rate	0.25%
Aggregate principal amount	$ 661,300
Additional aggregate principal	86,300
Net proceeds from sale of the notes	$ 645,500
Initial conversion rate (in shares)	0.003506
Initial conversion price (in dollars per share) | $ / shares	$ 285.26
Percent of the principal amount	100.00%
2026 ("Notes") | Convertible Debt | Conversion Period One
Schedule of Borrowings [Line Items]
Trading days | day	20
Consecutive trading days | optionToExtend	30
Conversion price maximum threshold	130.00%
2026 ("Notes") | Convertible Debt | Conversion Period Two
Schedule of Borrowings [Line Items]
Trading days | optionToExtend	5
Consecutive trading days | optionToExtend	5
Percentage of the last reported sale price	98.00%
2026 ("Notes") | Convertible Debt | Conversion Period Three
Schedule of Borrowings [Line Items]
Redemption price (in percent)	100.00%
Trading days | day	20
Consecutive trading days | day	30
Conversion price maximum threshold	130.00%
Gross debt issuance cost				15,700
Coupon interest expense				400
Amortization of debt issuance costs				$ 800
Effective interest rate				0.70%
London Interbank Offered Rate (LIBOR) | ULT Warehouse Credit Facility | Minimum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Basis spread on variable rate (in percent)			1.90%
London Interbank Offered Rate (LIBOR) | ULT Warehouse Credit Facility | Maximum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Basis spread on variable rate (in percent)			400.00%
Weighted-Average Cost Of Commercial Paper Notes Issued By The Lender | UAWT Warehouse Credit Facility | Minimum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Basis spread on variable rate (in percent)		1.80%
Weighted-Average Cost Of Commercial Paper Notes Issued By The Lender | UAWT Warehouse Credit Facility | Maximum | Revolving Credit Facility
Schedule of Borrowings [Line Items]
Basis spread on variable rate (in percent)		3.50%