Loans - Additional Information (Details)	6 Months Ended		12 Months Ended	54 Months Ended	102 Months Ended
	Nov. 30, 2021 USD ($) borrower loan state power_supply_system distribution_system	Nov. 30, 2020 USD ($)	May 31, 2021 USD ($) borrower power_supply_system state distribution_system	Nov. 30, 2021 USD ($) borrower loan power_supply_system distribution_system	Nov. 30, 2021 USD ($) borrower loan power_supply_system distribution_system
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans receivable cost of loans sold	$ 4,000,000	$ 96,000,000
Allowance for credit losses for accrued interest receivable	94,000,000		$ 93,000,000	$ 94,000,000	$ 94,000,000
Outstanding amount	$ 28,934,814,000	27,051,163,000	$ 28,415,107,000	$ 28,934,814,000	$ 28,934,814,000
Number of borrowers | borrower	892		892	892	892
Number of states in which electric and telecommunications borrowers are located | state	49		49
Number of loans outstanding | loan	16,512			16,512	16,512
Nonaccrual Loans	$ 219,444,000		$ 237,497,000	$ 219,444,000	$ 219,444,000
Financing receivable, troubled debt restructuring, commitment to lend	$ 0		$ 0	$ 0	$ 0
% of total loans outstanding	100.00%		100.00%	100.00%	100.00%
Financing receivable, allowance for credit loss, writeoff	$ 0	0
Term of loans	35 years
Loans originated prior to 2018	$ 17,121,974,000			$ 17,121,974,000	$ 17,121,974,000
Percentage of loans originated prior to 2018	59.00%			59.00%	59.00%
Financing receivable, before allowance for credit loss, average remaining maturity	18 years
Number of loans outstanding per borrower | loan	19			19	19
Line of credit commitments as percentage of unadvanced loan commitment	61.00%			61.00%	61.00%
Long-term loan commitments as percentage of unadvanced loan commitment	39.00%			39.00%	39.00%
Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 85,529,000		$ 84,996,000	$ 85,529,000	$ 85,529,000
Nonperforming TDR loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, troubled debt restructuring	0		0	0	0
Nonperforming financial instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 219,444,000		$ 237,497,000	$ 219,444,000	$ 219,444,000
Number of borrowers | borrower	2		4	2	2
Increase in nonaccrual loans		$ (18,000,000)
Nonaccrual Loans	$ 219,000,000		$ 237,000,000	$ 219,000,000	$ 219,000,000
% of total loans outstanding	0.76%		0.84%	0.76%	0.76%
Number of borrowers, nonperforming loans | borrower	2		4
Nonperforming financial instruments | RTFC Borrower One
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in finance receivables	$ (9,000,000)
Nonperforming financial instruments | RTFC Borrower Two
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in finance receivables	(9,000,000)
Criticized
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 890,137,000		$ 885,865,000	$ 890,137,000	$ 890,137,000
% of total loans outstanding	3.00%		3.00%	3.00%	3.00%
Loans originated prior to 2018	$ 247,592,000			$ 247,592,000	$ 247,592,000
Special mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	300,022,000		$ 269,387,000	300,022,000	300,022,000
Loans originated prior to 2018	52,635,000			52,635,000	52,635,000
Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	219,444,000		237,497,000	219,444,000	219,444,000
Loans originated prior to 2018	133,915,000			133,915,000	133,915,000
Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	370,671,000		378,981,000	370,671,000	370,671,000
Loans originated prior to 2018	61,042,000			61,042,000	61,042,000
Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	27,781,874,000		27,287,856,000	27,781,874,000	27,781,874,000
Nonaccrual Loans	$ 219,444,000		$ 228,312,000	$ 219,444,000	$ 219,444,000
% of total loans outstanding	96.00%		96.00%	96.00%	96.00%
Parent Company | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 85,529,000		$ 84,996,000	$ 85,529,000	$ 85,529,000
Parent Company | Brazos electric power cooperative | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of loans outstanding | loan	1			1	1
Parent Company | Special mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 295,680,000		264,795,000	$ 295,680,000	$ 295,680,000
Loans originated prior to 2018	48,293,000			48,293,000	48,293,000
Parent Company | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	219,444,000		228,312,000	219,444,000	219,444,000
Loans originated prior to 2018	133,915,000			133,915,000	133,915,000
Parent Company | Substandard | Rayburn country electric cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	371,000,000		379,000,000	371,000,000	371,000,000
RTFC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	431,641,000		420,383,000	431,641,000	431,641,000
Nonaccrual Loans	$ 0		$ 9,185,000	$ 0	$ 0
% of total loans outstanding	1.00%		1.00%	1.00%	1.00%
Financing receivable, allowance for credit loss, writeoff				$ 0
RTFC | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 0		$ 0	0	$ 0
RTFC | Nonperforming financial instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 0		$ 9,185,000	$ 0	$ 0
Number of borrowers | borrower			2
% of total loans outstanding	0.00%		0.03%	0.00%	0.00%
Number of borrowers, nonperforming loans | borrower	0		2
RTFC | Loan defaults
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 0			$ 0	$ 0
RTFC | Special mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	4,342,000		$ 4,592,000	4,342,000	4,342,000
Loans originated prior to 2018	4,342,000			4,342,000	4,342,000
RTFC | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	0		$ 9,185,000	0	0
Loans originated prior to 2018	$ 0			$ 0	$ 0
Geographic concentration risk | TEXAS | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of borrowers | borrower	68		67	68	68
Electric utility
Accounts, Notes, Loans and Financing Receivable [Line Items]
Financing receivable, allowance for credit loss, writeoff					$ 0
Electric utility | Loan defaults
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 0			$ 0	0
Electric utility | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan commitment term	5 years
Power supply | Nonperforming financial instruments | One CFC Electric Power Supply Borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 134,000,000		$ 143,000,000	134,000,000	134,000,000
Increase (decrease) in finance receivables	(9,000,000)
Power supply | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	5,122,406,000		5,154,312,000	5,122,406,000	5,122,406,000
Nonaccrual Loans	$ 219,444,000		$ 228,312,000	$ 219,444,000	$ 219,444,000
% of total loans outstanding	18.00%		18.00%	18.00%	18.00%
Power supply | Parent Company | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 85,529,000		$ 84,996,000	$ 85,529,000	$ 85,529,000
Power supply | Parent Company | Brazos electric power cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount			85,000,000
Power supply | Parent Company | Brazos electric power cooperative | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	86,000,000		85,000,000	86,000,000	86,000,000
Power supply | Parent Company | Nonperforming financial instruments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 219,444,000		$ 228,312,000	$ 219,444,000	$ 219,444,000
% of total loans outstanding	0.76%		0.81%	0.76%	0.76%
Number of borrowers, nonperforming loans | borrower	2		2
Power supply | Parent Company | Special mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 29,000,000		$ 29,611,000	$ 29,000,000	$ 29,000,000
Loans originated prior to 2018	29,000,000			29,000,000	29,000,000
Power supply | Parent Company | Doubtful
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	219,444,000		228,312,000	219,444,000	219,444,000
Loans originated prior to 2018	133,915,000			133,915,000	133,915,000
Power supply | Parent Company | Doubtful | Brazos electric power cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount			85,000,000
Power supply | Parent Company | Substandard
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	370,671,000		378,981,000	370,671,000	370,671,000
Loans originated prior to 2018	61,042,000			61,042,000	61,042,000
Distribution | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	22,558,077,000		22,027,423,000	22,558,077,000	22,558,077,000
Nonaccrual Loans	$ 0		$ 0	$ 0	$ 0
% of total loans outstanding	78.00%		78.00%	78.00%	78.00%
Distribution | Parent Company | Total Past Due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 0		$ 0	$ 0	$ 0
Distribution | Parent Company | Special mention
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	251,134,000		219,324,000	251,134,000	251,134,000
Loans originated prior to 2018	12,693,000			12,693,000	12,693,000
Distribution | Parent Company | Special mention | CFC electric distribution borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 251,000,000		219,000,000	$ 251,000,000	$ 251,000,000
Distribution | Parent Company | Special mention | CFC electric distribution borrower and subsidiary
Accounts, Notes, Loans and Financing Receivable [Line Items]
Number of borrowers | borrower	1			1	1
RTFC | Nonperforming financial instruments | RTFC Borrower
Accounts, Notes, Loans and Financing Receivable [Line Items]
Increase (decrease) in finance receivables	$ (18,000,000)
Unadvanced commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	14,678,351,000		14,357,039,000	$ 14,678,351,000	$ 14,678,351,000
Unadvanced commitments | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	13,743,795,000		13,519,108,000	13,743,795,000	13,743,795,000
Unadvanced commitments | RTFC
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	337,652,000		286,806,000	337,652,000	337,652,000
Unadvanced commitments | Power supply | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	3,904,003,000		3,970,698,000	3,904,003,000	3,904,003,000
Unadvanced commitments | Distribution | Parent Company
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	9,659,640,000		9,387,070,000	9,659,640,000	9,659,640,000
Commitments to extend credit subject to material adverse change clause
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	11,447,000,000		11,312,000,000	11,447,000,000	11,447,000,000
Unadvanced commitments not subject to material adverse change clauses
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	3,231,160,000		3,045,000,000	3,231,160,000	3,231,160,000
Nonperforming financial instruments | Power supply | Parent Company | Brazos electric power cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	86,000,000		85,000,000	86,000,000	86,000,000
Variable rate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 690,177,000		$ 658,579,000	$ 690,177,000	$ 690,177,000
% of total loans outstanding	2.00%		2.00%	2.00%	2.00%
Variable rate | Unadvanced commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan commitment term	5 years
Unadvanced commitments	$ 5,663,645,000		$ 5,771,813,000	$ 5,663,645,000	$ 5,663,645,000
Loans receivable commercial and industrial | Geographic concentration risk | TEXAS | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 4,975,000,000		$ 4,878,000,000	$ 4,975,000,000	$ 4,975,000,000
Concentration risk, percentage	17.00%		17.00%
Loans receivable commercial and industrial | Credit concentration risk | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, number of borrowers | borrower	20		20	20	20
Loans receivable commercial and industrial | Customer concentration risk | Twenty largest borrowers | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 6,134,000,000		$ 6,182,000,000	$ 6,134,000,000	$ 6,134,000,000
Concentration risk, percentage	21.00%		22.00%
Concentration risk, number of borrowers | borrower	20		20	20	20
Loans receivable commercial and industrial | Customer concentration risk | Largest single borrower or controlled group | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	2.00%		2.00%
Loans receivable commercial and industrial | Electric utility | Credit concentration risk | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 28,503,000,000		$ 27,995,000,000	$ 28,503,000,000	$ 28,503,000,000
Loans receivable commercial and industrial | Power supply | Customer concentration risk | Twenty largest borrowers | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, number of borrowers | power_supply_system	9		10	9	9
Loans receivable commercial and industrial | Distribution | Customer concentration risk | Twenty largest borrowers | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, number of borrowers | distribution_system	11		10	11	11
Loans guaranteed by Farmer Mac
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 486,000,000		$ 512,000,000	$ 486,000,000	$ 486,000,000
Financing receivable, before allowance for credit loss, number of defaults | loan	0			0	0
Financing receivable, before allowance for credit loss, number of defaulted loans purchased | loan	0			0	0
Loans guaranteed by Farmer Mac | Geographic concentration risk | TEXAS | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 167,000,000		172,000,000	$ 167,000,000	$ 167,000,000
Loans guaranteed by Farmer Mac | Credit concentration risk | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 255,000,000		$ 309,000,000	255,000,000	255,000,000
Concentration risk, percentage	20.00%		21.00%
Loans guaranteed by rural utilities service
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 135,000,000		$ 139,000,000	135,000,000	135,000,000
Loans and finance receivables | Credit concentration risk | Accounts receivable
Accounts, Notes, Loans and Financing Receivable [Line Items]
Concentration risk, percentage	99.00%		99.00%
Secured loans | Parent Company | Substandard | Rayburn country electric cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 159,000,000			159,000,000	159,000,000
Unsecured loans | Parent Company | Substandard | Rayburn country electric cooperative
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	212,000,000			212,000,000	212,000,000
Long-term loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Outstanding amount	$ 26,703,318,000		$ 26,173,345,000	$ 26,703,318,000	$ 26,703,318,000
% of total loans outstanding	92.00%		92.00%	92.00%	92.00%
Long-term loans | Unadvanced commitments
Accounts, Notes, Loans and Financing Receivable [Line Items]
Unadvanced commitments	$ 5,663,645,000		$ 5,771,813,000	$ 5,663,645,000	$ 5,663,645,000