Guarantees - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Dec. 31, 2020
Total
Total	$ 7,796,712		$ 7,796,712		$ 7,261,933
Rural Utilities
Year One
Total	21,022		21,022		667,489
Current period charge-offs	0	$ 0	0	$ 0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Two
Total	658,542		658,542		809,921
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Three
Total	792,333		792,333		8,260
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Four
Total	8,180		8,180		89,842
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Five
Total	89,488		89,488		31,275
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Prior
Total	648,818		648,818		641,145
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Revolving Loans - Amortized Cost Basis
Total	28,185		28,185		12,480
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total	2,246,568		2,246,568		2,260,412
Farm & Ranch
Year One
Total	1,128,706		1,128,706		2,021,189
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Two
Total	1,970,079		1,970,079		859,880
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Three
Total	764,412		764,412		524,541
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Four
Total	454,171		454,171		562,007
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Five
Total	418,099		418,099		515,561
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Prior
Total	1,334,124		1,334,124		1,140,603
Current period charge-offs	0	394	0	394
Current period recoveries	0	0	0	0
Current period, net charge offs	0	394	0	394
Revolving Loans - Amortized Cost Basis
Total	531,614		531,614		552,657
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total
Current period charge-offs	0	394	0	394
Current period recoveries	0	0	0	0
Current period, net charge offs	0	394	0	394
Total	6,601,205		6,601,205		6,176,438
Acceptable | Rural Utilities
Year One
Total	21,022		21,022		667,489
Year Two
Total	635,342		635,342		809,921
Year Three
Total	792,333		792,333		8,260
Year Four
Total	8,180		8,180		89,842
Year Five
Total	89,488		89,488		31,275
Prior
Total	648,818		648,818		641,145
Revolving Loans - Amortized Cost Basis
Total	28,185		28,185		12,480
Total
Total	2,223,368		2,223,368		2,260,412
Acceptable | Farm & Ranch
Year One
Total	1,085,630		1,085,630		1,947,618
Year Two
Total	1,873,579		1,873,579		774,315
Year Three
Total	704,749		704,749		484,345
Year Four
Total	409,047		409,047		500,768
Year Five
Total	364,489		364,489		465,277
Prior
Total	1,232,910		1,232,910		1,068,693
Revolving Loans - Amortized Cost Basis
Total	511,353		511,353		535,742
Total
Total	6,181,757		6,181,757		5,776,758
Special mention | Rural Utilities
Year One
Total	0		0		0
Year Two
Total	0		0		0
Year Three
Total	0		0		0
Year Four
Total	0		0		0
Year Five
Total	0		0		0
Prior
Total	0		0		0
Revolving Loans - Amortized Cost Basis
Total	0		0		0
Total
Total	0		0		0
Special mention | Farm & Ranch
Year One
Total	43,076		43,076		70,171
Year Two
Total	92,886		92,886		79,744
Year Three
Total	33,544		33,544		18,317
Year Four
Total	14,643		14,643		8,530
Year Five
Total	3,809		3,809		13,111
Prior
Total	16,706		16,706		21,328
Revolving Loans - Amortized Cost Basis
Total	8,826		8,826		7,656
Total
Total	213,490		213,490		218,857
Substandard | Rural Utilities
Year One
Total	0		0		0
Year Two
Total	23,200		23,200		0
Year Three
Total	0		0		0
Year Four
Total	0		0		0
Year Five
Total	0		0		0
Prior
Total	0		0		0
Revolving Loans - Amortized Cost Basis
Total	0		0		0
Total
Total	23,200		23,200		0
Substandard | Farm & Ranch
Year One
Total	0		0		3,400
Year Two
Total	3,614		3,614		5,821
Year Three
Total	26,119		26,119		21,879
Year Four
Total	30,481		30,481		52,709
Year Five
Total	49,801		49,801		37,173
Prior
Total	84,508		84,508		50,582
Revolving Loans - Amortized Cost Basis
Total	11,435		11,435		9,259
Total
Total	205,958		205,958		180,823
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch
Year One
Total	176,513		176,513		182,397
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Two
Total	275,039		275,039		225,612
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Three
Total	199,478		199,478		198,061
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Four
Total	194,972		194,972		257,223
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Five
Total	232,127		232,127		234,781
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Prior
Total	1,163,601		1,163,601		1,080,466
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Revolving Loans - Amortized Cost Basis
Total	213,217		213,217		226,203
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total	2,454,947		2,454,947		2,404,743
LTSPCs and Farmer Mac Guaranteed Securities | Acceptable | Farm & Ranch
Year One
Total	176,513		176,513		178,213
Year Two
Total	270,877		270,877		213,620
Year Three
Total	198,404		198,404		183,948
Year Four
Total	181,287		181,287		237,042
Year Five
Total	217,421		217,421		207,296
Prior
Total	1,040,596		1,040,596		969,860
Revolving Loans - Amortized Cost Basis
Total	201,691		201,691		211,620
Total
Total	2,286,789		2,286,789		2,201,599
LTSPCs and Farmer Mac Guaranteed Securities | Special mention | Farm & Ranch
Year One
Total	0		0		3,920
Year Two
Total	3,920		3,920		1,742
Year Three
Total	343		343		1,502
Year Four
Total	2,117		2,117		5,603
Year Five
Total	433		433		19,644
Prior
Total	60,494		60,494		50,004
Revolving Loans - Amortized Cost Basis
Total	7,683		7,683		10,058
Total
Total	74,990		74,990		92,473
LTSPCs and Farmer Mac Guaranteed Securities | Substandard | Farm & Ranch
Year One
Total	0		0		264
Year Two
Total	242		242		10,250
Year Three
Total	731		731		12,611
Year Four
Total	11,568		11,568		14,578
Year Five
Total	14,273		14,273		7,841
Prior
Total	62,511		62,511		60,602
Revolving Loans - Amortized Cost Basis
Total	3,843		3,843		4,525
Total
Total	93,168		93,168		110,671
LTSPCs | Rural Utilities
Year One
Total	0		0		0
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Two
Total	0		0		0
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Three
Total	0		0		0
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Four
Total	0		0		0
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Year Five
Total	0		0		0
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Prior
Total	520,145		520,145		549,405
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Revolving Loans - Amortized Cost Basis
Total	13,314		13,314		7,020
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	0	0	0
Total
Current period charge-offs	0	0	0	0
Current period recoveries	0	0	0	0
Current period, net charge offs	0	$ 0	0	$ 0
Total	533,459		533,459		556,425
LTSPCs | Acceptable | Rural Utilities
Year One
Total	0		0		0
Year Two
Total	0		0		0
Year Three
Total	0		0		0
Year Four
Total	0		0		0
Year Five
Total	0		0		0
Prior
Total	520,145		520,145		549,405
Revolving Loans - Amortized Cost Basis
Total	13,314		13,314		7,020
Total
Total	533,459		533,459		556,425
LTSPCs | Special mention | Rural Utilities
Year One
Total	0		0		0
Year Two
Total	0		0		0
Year Three
Total	0		0		0
Year Four
Total	0		0		0
Year Five
Total	0		0		0
Prior
Total	0		0		0
Revolving Loans - Amortized Cost Basis
Total	0		0		0
Total
Total	0		0		0
LTSPCs | Substandard | Rural Utilities
Year One
Total	0		0		0
Year Two
Total	0		0		0
Year Three
Total	0		0		0
Year Four
Total	0		0		0
Year Five
Total	0		0		0
Prior
Total	0		0		0
Revolving Loans - Amortized Cost Basis
Total	0		0		0
Total
Total	$ 0		$ 0		$ 0