Guarantees - Credit Quality Indicators (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Total
Gross financing receivables	$ 7,148,108
Gross financing receivables	7,148,108
Financing receivables, past due	29,997
Off-Balance Sheet:
Total
Gross financing receivables			$ 2,500,393
Gross financing receivables			2,500,393
Financing receivables, past due			3,235
Off-Balance Sheet: | Crops
Total
Gross financing receivables			1,157,681
Gross financing receivables			1,157,681
Financing receivables, past due			1,493
Off-Balance Sheet: | Permanent Plantings
Total
Gross financing receivables			514,105
Gross financing receivables			514,105
Financing receivables, past due			196
Off-Balance Sheet: | Livestock
Total
Gross financing receivables			591,584
Gross financing receivables			591,584
Financing receivables, past due			1,066
Off-Balance Sheet: | Part-time Farm
Total
Gross financing receivables			168,101
Gross financing receivables			168,101
Financing receivables, past due			480
Off-Balance Sheet: | Ag. Storage and Processing
Total
Gross financing receivables			66,106
Gross financing receivables			66,106
Financing receivables, past due			0
Off-Balance Sheet: | Other
Total
Gross financing receivables			2,816
Gross financing receivables			2,816
Financing receivables, past due			0
Farm & Ranch
2020
Total	296,887
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2019
Total	983,174
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2018
Total	642,485
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2017
Total	767,993
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2016
Total	629,878
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Prior
Total	1,549,183
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Revolving Loans - Amortized Cost Basis
Total	488,782
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Total
Gross financing receivables	5,358,382
Current period charge-offs	0	$ 0
Current period recoveries	0
Current period net charge-offs	0
Gross financing receivables	5,358,382
Financing receivables, past due	29,997
Rural  Utilities
2020
Total	152,385
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2019
Total	836,763
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2018
Total	8,337
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2017
Total	92,568
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
2016
Total	31,829
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Prior
Total	667,844
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Revolving Loans - Amortized Cost Basis
Total	0
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Total
Gross financing receivables	1,789,726
Current period charge-offs	0	$ 0
Current period recoveries	0
Current period net charge-offs	0
Gross financing receivables	1,789,726
Financing receivables, past due	0
Acceptable | Off-Balance Sheet:
Total
Gross financing receivables			2,269,005
Gross financing receivables			2,269,005
Acceptable | Off-Balance Sheet: | Crops
Total
Gross financing receivables			1,033,002
Gross financing receivables			1,033,002
Acceptable | Off-Balance Sheet: | Permanent Plantings
Total
Gross financing receivables			484,601
Gross financing receivables			484,601
Acceptable | Off-Balance Sheet: | Livestock
Total
Gross financing receivables			521,341
Gross financing receivables			521,341
Acceptable | Off-Balance Sheet: | Part-time Farm
Total
Gross financing receivables			161,361
Gross financing receivables			161,361
Acceptable | Off-Balance Sheet: | Ag. Storage and Processing
Total
Gross financing receivables			66,106
Gross financing receivables			66,106
Acceptable | Off-Balance Sheet: | Other
Total
Gross financing receivables			2,594
Gross financing receivables			2,594
Acceptable | Farm & Ranch
2020
Total	286,971
2019
Total	819,220
2018
Total	588,761
2017
Total	688,649
2016
Total	555,678
Prior
Total	1,452,711
Revolving Loans - Amortized Cost Basis
Total	468,114
Total
Gross financing receivables	4,860,104
Gross financing receivables	4,860,104
Acceptable | Rural  Utilities
2020
Total	152,385
2019
Total	836,763
2018
Total	8,337
2017
Total	92,568
2016
Total	31,829
Prior
Total	662,830
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	1,784,712
Gross financing receivables	1,784,712
Special mention(1) | Off-Balance Sheet:
Total
Gross financing receivables			128,511
Gross financing receivables			128,511
Special mention(1) | Off-Balance Sheet: | Crops
Total
Gross financing receivables			68,372
Gross financing receivables			68,372
Special mention(1) | Off-Balance Sheet: | Permanent Plantings
Total
Gross financing receivables			22,909
Gross financing receivables			22,909
Special mention(1) | Off-Balance Sheet: | Livestock
Total
Gross financing receivables			35,618
Gross financing receivables			35,618
Special mention(1) | Off-Balance Sheet: | Part-time Farm
Total
Gross financing receivables			1,612
Gross financing receivables			1,612
Special mention(1) | Off-Balance Sheet: | Ag. Storage and Processing
Total
Gross financing receivables			0
Gross financing receivables			0
Special mention(1) | Off-Balance Sheet: | Other
Total
Gross financing receivables			0
Gross financing receivables			0
Special mention(1) | Farm & Ranch
2020
Total	9,916
2019
Total	159,523
2018
Total	36,786
2017
Total	20,937
2016
Total	32,227
Prior
Total	18,283
Revolving Loans - Amortized Cost Basis
Total	9,230
Total
Gross financing receivables	286,902
Gross financing receivables	286,902
Special mention(1) | Rural  Utilities
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	0
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	0
Gross financing receivables	0
Substandard(2) | Off-Balance Sheet:
Total
Gross financing receivables			102,877
Gross financing receivables			102,877
Substandard(2) | Off-Balance Sheet: | Crops
Total
Gross financing receivables			56,307
Gross financing receivables			56,307
Substandard(2) | Off-Balance Sheet: | Permanent Plantings
Total
Gross financing receivables			6,595
Gross financing receivables			6,595
Substandard(2) | Off-Balance Sheet: | Livestock
Total
Gross financing receivables			34,625
Gross financing receivables			34,625
Substandard(2) | Off-Balance Sheet: | Part-time Farm
Total
Gross financing receivables			5,128
Gross financing receivables			5,128
Substandard(2) | Off-Balance Sheet: | Ag. Storage and Processing
Total
Gross financing receivables			0
Gross financing receivables			0
Substandard(2) | Off-Balance Sheet: | Other
Total
Gross financing receivables			222
Gross financing receivables			$ 222
Substandard(2) | Farm & Ranch
2020
Total	0
2019
Total	4,431
2018
Total	16,938
2017
Total	58,407
2016
Total	41,973
Prior
Total	78,189
Revolving Loans - Amortized Cost Basis
Total	11,438
Total
Gross financing receivables	211,376
Gross financing receivables	211,376
Substandard(2) | Rural  Utilities
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	5,014
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	5,014
Gross financing receivables	5,014
LTSPCs and Farmer Mac Guaranteed Securities | Farm & Ranch
2020
Total	31,243
Current period net charge-offs	0
2019
Total	222,942
Current period net charge-offs	0
2018
Total	194,464
Current period net charge-offs	0
2017
Total	295,439
Current period net charge-offs	0
2016
Total	259,230
Current period net charge-offs	0
Prior
Total	1,261,712
Current period net charge-offs	0
Revolving Loans - Amortized Cost Basis
Total	188,182
Current period net charge-offs	0
Total
Gross financing receivables	2,453,212
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Gross financing receivables	2,453,212
Financing receivables, past due	18,681
LTSPCs and Farmer Mac Guaranteed Securities | Acceptable | Farm & Ranch
2020
Total	31,243
2019
Total	219,342
2018
Total	183,228
2017
Total	249,022
2016
Total	225,466
Prior
Total	1,132,870
Revolving Loans - Amortized Cost Basis
Total	173,082
Total
Gross financing receivables	2,214,253
Gross financing receivables	2,214,253
LTSPCs and Farmer Mac Guaranteed Securities | Special mention(1) | Farm & Ranch
2020
Total	0
2019
Total	3,600
2018
Total	7,843
2017
Total	29,982
2016
Total	17,482
Prior
Total	68,709
Revolving Loans - Amortized Cost Basis
Total	10,379
Total
Gross financing receivables	137,995
Gross financing receivables	137,995
LTSPCs and Farmer Mac Guaranteed Securities | Substandard(2) | Farm & Ranch
2020
Total	0
2019
Total	0
2018
Total	3,393
2017
Total	16,435
2016
Total	16,282
Prior
Total	60,133
Revolving Loans - Amortized Cost Basis
Total	4,721
Total
Gross financing receivables	100,964
Gross financing receivables	100,964
LTSPCs | Rural  Utilities
2020
Total	0
Current period net charge-offs	0
2019
Total	0
Current period net charge-offs	0
2018
Total	0
Current period net charge-offs	0
2017
Total	0
Current period net charge-offs	0
2016
Total	0
Current period net charge-offs	0
Prior
Total	595,685
Current period net charge-offs	0
Revolving Loans - Amortized Cost Basis
Total	0
Current period net charge-offs	0
Total
Gross financing receivables	595,685
Current period charge-offs	0
Current period recoveries	0
Current period net charge-offs	0
Gross financing receivables	595,685
Financing receivables, past due	0
LTSPCs | Acceptable | Rural  Utilities
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	595,685
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	595,685
Gross financing receivables	595,685
LTSPCs | Special mention(1) | Rural  Utilities
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	0
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	0
Gross financing receivables	0
LTSPCs | Substandard(2) | Rural  Utilities
2020
Total	0
2019
Total	0
2018
Total	0
2017
Total	0
2016
Total	0
Prior
Total	0
Revolving Loans - Amortized Cost Basis
Total	0
Total
Gross financing receivables	0
Gross financing receivables	$ 0