v3.26.1
Loans and Allowance for Credit Losses - Summary of Inclusive Capitalized Loans (Detail) - USD ($)
$ in Thousands
 6 Months Ended 12 Months Ended
Jun. 30, 2026
Dec. 31, 2025
Mar. 31, 2026
Jun. 30, 2025
Mar. 31, 2025
Dec. 31, 2024
Student Loan Portfolio By Program [Line Items]            
Total loans $ 2,773,366 $ 2,551,705        
Loans held for sale, at lower of amortized cost or fair value 21,376 15,144        
Total loans, gross 2,650,665 2,436,916        
Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 2,794,742 2,566,849 $ 2,617,995 $ 2,485,051 $ 2,486,433 $ 2,491,022
Total loans, gross $ 2,794,742 $ 2,566,849        
Percentage of total gross loans [1] 100.00% 100.00%        
Bank Holding Company Accounting [Member] | Loans Held for Investment [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 2,773,366 $ 2,551,705        
Percentage of total gross loans [1] 99.00% 99.00%        
Bank Holding Company Accounting [Member] | Loans Held for Sale at Lower of Amortized Cost or Fair Value [Member]            
Student Loan Portfolio By Program [Line Items]            
Loans held for sale, at lower of amortized cost or fair value $ 21,376 $ 15,144        
Recreation [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 1,760,297 1,617,221        
Recreation [Member] | Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 1,760,297 1,617,221 1,671,538 1,546,252 [2] 1,545,844 [2] 1,543,243 [3]
Recreation [Member] | Bank Holding Company Accounting [Member] | Loans Held for Investment [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 1,760,297 $ 1,617,221        
Percentage of total gross loans [1] 63.00% 63.00%        
Home Improvement [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 885,599 $ 810,237        
Home Improvement [Member] | Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 885,599 810,237 814,933 803,535 812,381 827,211
Home Improvement [Member] | Bank Holding Company Accounting [Member] | Loans Held for Investment [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 885,599 $ 810,237        
Percentage of total gross loans [1] 32.00% 32.00%        
Commercial [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 126,177 $ 123,068        
Commercial [Member] | Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 126,177 123,068 119,612 121,415 116,059 111,273
Commercial [Member] | Bank Holding Company Accounting [Member] | Loans Held for Investment [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 126,177 $ 123,068        
Percentage of total gross loans [1] 5.00% 5.00%        
Taxi Medallion [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans $ 1,293 $ 1,179        
Taxi Medallion [Member] | Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 1,293 1,179 1,126 1,564 1,650 1,909
Taxi Medallion [Member] | Bank Holding Company Accounting [Member] | Loans Held for Investment [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 1,293 1,179        
Strategic Partnership [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 21,376 15,144        
Strategic Partnership [Member] | Bank Holding Company Accounting [Member]            
Student Loan Portfolio By Program [Line Items]            
Total loans 21,376 15,144 $ 10,786 $ 12,285 $ 10,499 $ 7,386
Strategic Partnership [Member] | Bank Holding Company Accounting [Member] | Loans Held for Sale at Lower of Amortized Cost or Fair Value [Member]            
Student Loan Portfolio By Program [Line Items]            
Loans held for sale, at lower of amortized cost or fair value $ 21,376 $ 15,144        
[1]

(1) Percentage may not foot due to rounding.
[2] Includes loans held for sale and loans held for investment.
[3] Includes loans held for sale and loans held for investment.