BASIS OF PRESENTATION AND SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES - Narrative (Details) $ / shares in Units, $ in Thousands			1 Months Ended	3 Months Ended	12 Months Ended
		Jun. 13, 2025 USD ($) $ / shares shares	Apr. 30, 2025	Jun. 30, 2025 shares	Dec. 31, 2025 USD ($) segment period shares	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Common stock, authorized (in shares) | shares					0	416,094,141
Preferred stock, authorized (in shares) | shares					100,000,000	0
Number of operating segments | segment					1
Number of reportable segments | segment					1
Advertising costs | $					$ 509,800	$ 456,600	$ 394,700
Termination costs | $					$ 32,600
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]					General and administrative
Goodwill | $					$ 27,492	27,492
Contributions | $					9,500	8,500	8,400
Marketable securities | $					587,828	368,889
Repurchases of common stock | $					$ (77,538)	$ (853)	(55)
Service-based RSUs
Summary Of Significant Accounting Policies [Line Items]
Vesting period					4 years
Market-based PSUs
Summary Of Significant Accounting Policies [Line Items]
Vesting period			4 years
Number of service periods | period					2
Accounts Receivable | Customer Concentration Risk | Combined Bank Partners
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					46.00%	45.00%
Accounts Receivable | Customer Concentration Risk | Bank Partner A
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					26.00%	25.00%
Accounts Receivable | Customer Concentration Risk | Bank Partner B
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					20.00%	20.00%
Accounts Receivable | Customer Concentration Risk | Card Network Partner
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					50.00%	50.00%
U.S. government securities
Summary Of Significant Accounting Policies [Line Items]
Marketable securities | $					$ 563,594	$ 352,627
U.S. government securities | Debt Securities | Security Concentration Risk
Summary Of Significant Accounting Policies [Line Items]
Concentration risk, percentage					96.00%	96.00%
Internal-use software
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life					3 years
Common Stock
Summary Of Significant Accounting Policies [Line Items]
Conversion of redeemable convertible preferred stock to common stock in connection with initial public offering (in shares) | shares	[1]	258,667,796		258,667,796	258,667,796
Additional Paid-in Capital
Summary Of Significant Accounting Policies [Line Items]
Repurchases of common stock | $					$ (77,538)	$ (853)	$ (55)
Common Class A
Summary Of Significant Accounting Policies [Line Items]
Shares converted (in shares) | shares		32,182,289
Common stock, authorized (in shares) | shares		5,000,000,000.0			5,000,000,000	0
Common Class B
Summary Of Significant Accounting Policies [Line Items]
Common stock, authorized (in shares) | shares		65,000,000.0			65,000,000	0
Class C common stock
Summary Of Significant Accounting Policies [Line Items]
Common stock, authorized (in shares) | shares		500,000,000.0			500,000,000	0
Preferred Stock
Summary Of Significant Accounting Policies [Line Items]
Preferred stock, authorized (in shares) | shares		100,000,000.0
IPO
Summary Of Significant Accounting Policies [Line Items]
Number of shares sold by stockholders (in shares) | shares		6,099,235
Number of shares sold by company (in shares) | shares		4,800,000
Consideration received on transaction | $		$ 770,600
Discounts and commissions | $		43,500
Offering expenses | $		$ 14,800
IPO | Common Class A
Summary Of Significant Accounting Policies [Line Items]
Sale of stock, number of shares (in shares) | shares		36,800,000
Sale of stock, price per share (in usd per share) | $ / shares		$ 27.00

[1] The share amounts listed above combine common stock, Class A common stock and Class B common stock. In connection with the completion of our initial public offering, all previously outstanding shares of common stock were reclassified into Class A common stock and Class B common stock. Refer to Note 2 for more information.