Loans - Unpaid Principal Balances by Delinquency Status (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 8,481,310	$ 8,314,096
Nonaccrual loans	120,705	126,807
Total Loans	9,484,080	9,236,129
Nonaccrual loans with no associated allowance	34,900	31,000
Interest received on nonaccrual loans	1,800	5,000
Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	6,932,229	6,846,993
Nonaccrual loans	120,705	126,807
Total Loans	6,932,229	6,846,993
Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	2,551,851	2,389,136
Nonaccrual loans	0	0
Total Loans	2,551,851	2,389,136
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	9,349,595	9,104,206
Current | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	6,797,744	6,715,070
Current | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	2,551,851	2,389,136
Total Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	13,780	5,116
Total Past Due | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	13,780	5,116
Total Past Due | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	0	0
30-59 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	4,624	4,548
30-59 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	4,624	4,548
30-59 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	0	0
60-89 Days
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	639	568
60-89 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	639	568
60-89 Days | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	0	0
90 Days and Greater
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	8,517	0
90 Days and Greater | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	8,517	0
90 Days and Greater | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total	$ 0	$ 0