LOANS - Unpaid Principal Balances by Delinquency Status (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	$ 9,837,962	$ 9,623,119
Nonaccrual loans	96,240	65,236
Total loans	11,602,199	11,360,197
Nonaccrual loans with no associated allowance	45,900	25,700
Interest received on nonaccrual loans	600	2,600
Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual loans	96,240	65,236
Total loans	7,915,446	7,825,434
Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,656,940	6,565,711
Nonaccrual loans	84,793	65,236
Total loans	6,656,940	6,565,711
Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	1,258,506	1,259,723
Nonaccrual loans	11,447	0
Total loans	1,258,506	1,259,723
Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,686,753	3,534,763
Nonaccrual loans	0	0
Total loans	3,686,753	3,534,763
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	11,472,618	11,264,691
Current | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	7,785,865	7,729,928
Current | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	6,538,806	6,470,205
Current | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	1,247,059	1,259,723
Current | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,686,753	3,534,763
Total Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	33,341	30,270
Total Past Due | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	33,341	30,270
Total Past Due | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	33,341	30,270
Total Past Due | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
Total Past Due | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
30-59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	13,764	15,326
30-59 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	13,764	15,326
30-59 Days | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	13,764	15,326
30-59 Days | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
30-59 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
60-89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,954	3,953
60-89 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,954	3,953
60-89 Days | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	3,954	3,953
60-89 Days | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
60-89 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
90 Days and Greater
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,623	10,991
90 Days and Greater | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,623	10,991
90 Days and Greater | Farm & Ranch
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	15,623	10,991
90 Days and Greater | Corporate AgFinance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	0	0
90 Days and Greater | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Loans held for investment, at amortized cost	$ 0	$ 0