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Held-to-Maturity Unpaid Principal Balance

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[Line Items] for Schedule of held to maturity, available for sale, and trading securities which includes, but is not limited to changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis and other related disclosures

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Trading Securities Unpaid Principal Balance

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Trading Securities, Weighted-Average Yield

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Transfer of Farmer Mac Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains

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Transfer of Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains

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Transfer of USDA Guaranteed Securities- Available-for-sale to Held-to-maturity; Unrealized holding gains

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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Number of investment positions in available-for-sale investments that have been in a continuous unrealized loss position for greater than or equal to a year for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Amount before other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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Disclosure regarding factors used to determine that the impairment of securities categorized as held-to-maturity where cost exceeds fair value is not an other than temporary impairment (OTTI). This item contains disclosure of the number of investment positions in the held-to-maturity investments determined to be temporarily impaired.

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Amount of investments in debt and equity securities and other forms of securities that provide ownership interests classified as trading.

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Amortized cost of investments in debt securities classified as trading.

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Amount of unrealized holding gain before loss recognized in the income statement for investments in trading securities.

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Amount of unrealized holding loss before gain recognized in the income statement for investments in trading securities.

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Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Farmer Mac Guaranteed Securities and USDA Securities (Details) $ in Thousands			12 Months Ended
	Dec. 31, 2017 USD ($) position	Dec. 31, 2016 USD ($) position	Dec. 31, 2017 USD ($) position	Dec. 31, 2016 USD ($) position	Dec. 31, 2015 USD ($)	Oct. 01, 2016 USD ($)
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| position	91	97	91	97
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 2,106	$ 7,633	$ 2,106	$ 7,633
Transfer of USDA Guaranteed Securities- Available-for-sale to Held-to-maturity; Unrealized holding gains						$ 73,100
Trading Securities [Abstract]
Transfer of Farmer Mac Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains						700
Transfer of Farmer Mac Guaranteed Securities and USDA Guaranteed Securities - Available-for-sale to Held-to-maturity; Unrealized holding gains						$ 73,800
Farmer Mac Guaranteed Securities and USDA Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	62,340		62,340
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	4,181,784	3,086,504	4,181,784	3,086,504
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	4,244,124	3,158,456	4,244,124	3,158,456
Held to Maturity; Unrealized Holding Gains	2,119	7,192	2,119	7,192
Held to Maturity - Unrealized Holding Loss	(66,471)	(99,004)	(66,471)	(99,004)
Held-to-maturity Securities, Fair Value	4,179,772	3,066,644	4,179,772	3,066,644
Available-for-sale Securities [Abstract]
Available-for-sale Securities, Amortized Cost Basis	5,496,387		5,496,387
Available-for-sale, at fair value	5,471,914		5,471,914
Farmer Mac Guaranteed Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	(460)	(1,833)	(460)	(1,833)
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	2,126,734	1,151,064	2,126,734	1,151,064
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	2,126,274	1,149,231	2,126,274	1,149,231
Held to Maturity; Unrealized Holding Gains	2,119	7,192	2,119	7,192
Held to Maturity - Unrealized Holding Loss	(11,502)	(3,414)	(11,502)	(3,414)
Held-to-maturity Securities, Fair Value	2,116,891	1,153,009	2,116,891	1,153,009
USDA Securities [Member]
Trading Securities [Abstract]
Trading, at fair value	$ 13,515	20,388	$ 13,515	20,388
Institutional Credit [Member] \| Farmer Mac Guaranteed Securities and USDA Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)		$ 71,952		$ 71,952
Institutional Credit [Member] \| Farmer Mac Guaranteed Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| position	36	22	36	22
Held-to-maturity, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions \| position	23	7	23	7
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions, Greater than or Equal to One Year \| position	16	10	16	10
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss	$ 37,492	$ 45,452	$ 37,492	$ 45,452
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	2,096,754	1,115,465	2,096,754	1,115,465
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	2,095,975	1,113,189	2,095,975	1,113,189
Held to Maturity; Unrealized Holding Gains	2,011	7,187	2,011	7,187
Held to Maturity - Unrealized Holding Loss	(11,429)	(3,175)	(11,429)	(3,175)
Held-to-maturity Securities, Fair Value	2,086,557	1,117,201	2,086,557	1,117,201
Available-for-sale Securities [Abstract]
Available-for-Sale Securities Unpaid Principal Balance	5,496,569	4,889,007	5,496,569	4,889,007
Available-for-sale Securities, Amortized Cost Basis	5,496,387	4,888,904	5,496,387	4,888,904
Available-for-sale Debt Securities, Accumulated Gross Unrealized Gain, before Tax	21,838	28,715	21,838	28,715
Available-for-sale Securities, Unrealized Losses	(46,311)	(63,934)	(46,311)	(63,934)
Available-for-sale, at fair value	5,471,914	4,853,685	5,471,914	4,853,685
Institutional Credit [Member] \| Held-to-maturity Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	(779)	(2,276)	(779)	(2,276)
Institutional Credit [Member] \| Available-for-sale Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	(182)	(103)	(182)	(103)
USDA Guarantees [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	300	400	300	400
USDA Guarantees [Member] \| Farmer Mac Guaranteed Securities [Member]
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	29,980	35,599	29,980	35,599
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	30,299	36,042	30,299	36,042
Held to Maturity; Unrealized Holding Gains	108	5	108	5
Held to Maturity - Unrealized Holding Loss	(73)	(239)	(73)	(239)
Held-to-maturity Securities, Fair Value	30,334	35,808	30,334	35,808
USDA Guarantees [Member] \| USDA Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	62,800	73,785	62,800	73,785
Held-to-Maturity Securities [Abstract]
Held-to-Maturity Unpaid Principal Balance	2,055,050	1,935,440	2,055,050	1,935,440
Held-to-maturity Securities, Amortized Cost before Other than Temporary Impairment	2,117,850	2,009,225	2,117,850	2,009,225
Held to Maturity; Unrealized Holding Gains	0	0	0	0
Held to Maturity - Unrealized Holding Loss	(54,969)	(95,590)	(54,969)	(95,590)
Held-to-maturity Securities, Fair Value	2,062,881	1,913,635	2,062,881	1,913,635
Trading Securities [Abstract]
Trading Securities Unpaid Principal Balance	12,966	19,360	12,966	19,360
Trading Securities, Debt, Amortized Cost	13,888	20,737	13,888	20,737
Trading Securities, Unrealized Gains	28	41
Trading Securities, Unrealized Holding Loss	(401)	(390)
Trading, at fair value	$ 13,515	$ 20,388	$ 13,515	$ 20,388
Trading Securities, Weighted-Average Yield	5.33%	5.44%	5.33%	5.44%
USDA Guarantees [Member] \| Available-for-sale Securities [Member] \| Farmer Mac Guaranteed Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	$ 319	$ 443	$ 319	$ 443
USDA Guarantees [Member] \| Trading Securities [Member] \| USDA Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Unamortized Premium/(Discount)	$ 922	$ 1,377	922	1,377
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				2,013,151
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Farmer Mac Guaranteed Securities [Member] \| Available-for-sale Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3			$ 0	32,824	$ 0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Farmer Mac Guaranteed Securities [Member] \| USDA Guarantee [Member] \| Available-for-sale Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				2,000,000
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Farmer Mac Guaranteed Securities [Member] \| Farmer Mac Guaranteed Securities [Member] \| Available-for-sale Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				32,800
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Farmer Mac Guaranteed Securities [Member] \| Institutional Credit [Member] \| Available-for-sale Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				0
Fair Value, Inputs, Level 3 [Member] \| Fair Value, Measurements, Recurring [Member] \| Farmer Mac Guaranteed Securities [Member] \| USDA Guarantees [Member] \| Available-for-sale Securities [Member]
Schedule of Held-to-Maturity, Available-for-sale, and Trading Securities [Line Items]
Fair Value, Measurement with Unobservable Inputs Reconciliation, Recurring Basis, Asset, Transfers out of Level 3				$ 32,824