Loans - Unpaid Principal Balances by Delinquency Status (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		$ 8,314,096	$ 7,261,933
Nonaccrual loans		126,807	114,998
Total Loans		9,236,129	8,436,850
Nonaccrual loans with no associated allowance		31,000	44,200
Interest received on nonaccrual loans	$ 4,400	5,000
Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		6,846,993	6,176,438
Nonaccrual loans		126,807	114,998
Total Loans		6,846,993	6,176,438
Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		2,389,136	2,260,412
Nonaccrual loans		0	0
Total Loans		2,389,136	2,260,412
Current
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		9,104,206	8,315,566
Current | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		6,715,070	6,055,154
Current | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		2,389,136	2,260,412
Total Past Due
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		5,116	6,286
Total Past Due | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		5,116	6,286
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		4,548	4,582
30-59 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		4,548	4,582
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		568	632
60-89 Days | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		568	632
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		0	1,072
90 Days and Greater | Agricultural Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		0	1,072
90 Days and Greater | Rural Infrastructure Finance
Financing Receivable, Recorded Investment, Past Due [Line Items]
Total		$ 0	$ 0