Fair Value Disclosures - Summary of Carrying Value and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Financial assets:
Financial derivatives	$ 13,623	$ 16,123
Guarantee and commitment fees receivable	37,261	37,113
Financial liabilities:
Financial derivatives	152,881	182,371
Guarantee and commitment obligation	35,827	35,535
Fair Value
Financial assets:
Cash and cash equivalents	828,403	1,033,941
Loans	9,057,544	9,167,525
Financial derivatives	16,224	17,468
Guarantee and commitment fees receivable	34,525	34,115
Financial liabilities:
Notes payable	21,839,641	22,130,263
Debt securities of consolidated trusts held by third parties	1,121,731	1,390,330
Financial derivatives	24,347	29,892
Guarantee and commitment obligation	33,091	32,537
Fair Value | Investment securities:
Financial assets:
Marketable securities	3,877,470	3,899,925
Fair Value | Farmer Mac Guaranteed Securities
Financial assets:
Marketable securities	7,931,395	8,148,691
Fair Value | USDA Securities:
Financial assets:
Marketable securities	2,472,043	2,637,509
Carrying Amount
Financial assets:
Cash and cash equivalents	828,403	1,033,941
Loans	8,860,705	8,535,146
Financial derivatives	16,224	17,468
Guarantee and commitment fees receivable	37,261	37,113
Financial liabilities:
Notes payable	21,706,254	21,848,917
Debt securities of consolidated trusts held by third parties	1,120,293	1,323,786
Financial derivatives	24,347	29,892
Guarantee and commitment obligation	35,827	35,535
Carrying Amount | Investment securities:
Financial assets:
Marketable securities	3,877,667	3,898,724
Carrying Amount | Farmer Mac Guaranteed Securities
Financial assets:
Marketable securities	7,918,162	8,123,493
Carrying Amount | USDA Securities:
Financial assets:
Marketable securities	$ 2,450,768	$ 2,480,321