Represents the percent of insured loans used as base for loans guaranteed by US Department of Education.

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- Definition

Reflects percentage of outstanding principal amount of loans guaranteed by US Department of Education.

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No definition available.

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

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No definition available.

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

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No definition available.

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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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No definition available.

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- Definition

Fair value at acquisition of acquired loans not accounted for as debt securities with evidence of deterioration of credit quality.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

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Amount of restricted investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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The cash outflow to acquire debt and equity securities not classified as either held-to-maturity securities or trading securities which would be classified as available-for-sale securities and reported at fair value, with unrealized gains and losses excluded from earnings and reported in a separate component of shareholders' equity.

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The cash inflow associated with the sale of debt and equity securities classified as available-for-sale securities.

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Securities - Amortized Cost and Fair Value (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Securities Available-for-Sale
Amortized Cost	$ 546,867	$ 537,645
Gross Unrealized Gains	3,229	8,467
Gross Unrealized Losses	(8,848)	(4,673)
Fair Value	541,248	541,439
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, at Acquisition, at Fair Value	10,965
Other disclosures
Purchases	75,044	343,470	$ 210,681
Sales	94,663	232,462	$ 306,400
Securities pledged to secure deposits and for other purposes	$ 318,400	301,000
Reimbursement requests greater than 5 %
Other disclosures
Percentage of outstanding principal amount of loans guaranteed by US Department of Education	85.00
Percent of insured loan	5.00
Reimbursement requests greater than 9 %
Other disclosures
Percentage of outstanding principal amount of loans guaranteed by US Department of Education	75.00
Percent of insured loan	9.00
U.S. Treasury
Securities Available-for-Sale
Amortized Cost	$ 4,006	4,002
Gross Unrealized Losses	(83)	(55)
Fair Value	3,923	3,947
US Treasury and Government
Securities Available-for-Sale
Amortized Cost	11,112
Gross Unrealized Losses	(161)
Fair Value	10,951
U.S. government agencies
Securities Available-for-Sale
Amortized Cost		13,062
Gross Unrealized Gains		8
Gross Unrealized Losses		(9)
Fair Value		13,061
U.S. government agencies mortgage-backed
Securities Available-for-Sale
Amortized Cost	14,407	12,372
Gross Unrealized Gains	45	7
Gross Unrealized Losses	(377)	(165)
Fair Value	14,075	12,214
States and political subdivisions
Securities Available-for-Sale
Amortized Cost	277,112	272,240
Gross Unrealized Gains	1,916	7,116
Gross Unrealized Losses	(4,961)	(1,264)
Fair Value	274,067	278,092
Corporate bonds
Securities Available-for-Sale
Amortized Cost		823
Gross Unrealized Gains		21
Gross Unrealized Losses		(11)
Fair Value		833
Collateralized mortgage obligations
Securities Available-for-Sale
Amortized Cost	66,494	66,892
Gross Unrealized Gains	79	202
Gross Unrealized Losses	(2,144)	(1,155)
Fair Value	64,429	65,939
Asset-backed securities
Securities Available-for-Sale
Amortized Cost	108,574	113,983
Gross Unrealized Gains	1,165	862
Gross Unrealized Losses	(225)	(1,913)
Fair Value	109,514	112,932
FFEL
Securities Available-for-Sale
Fair Value	$ 93,100
Other disclosures
Percentage of outstanding principal amount of loans guaranteed by US Department of Education	97.00
Collateralized loan obligations
Securities Available-for-Sale
Amortized Cost	$ 65,162	54,271
Gross Unrealized Gains	24	251
Gross Unrealized Losses	(897)	(101)
Fair Value	64,289	$ 54,421
GCO Education Loan Funding Corp
Securities Available-for-Sale
Amortized Cost	27,739
Fair Value	$ 27,763
GCO Education Loan Funding Corp \| Stockholders' Equity
Other disclosures
Credit risk as a percentage of benchmark	1.00%
Towd Point Mortgage Trust
Securities Available-for-Sale
Amortized Cost	$ 34,308
Fair Value	33,318
Student Marketing Association [Member]
Securities Available-for-Sale
Amortized Cost	25,808
Fair Value	26,119
Stockholders' Equity \| Asset-backed securities \| Credit Concentration Risk
Securities Available-for-Sale
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Acquired During Period, at Acquisition, at Fair Value	27,739
Stockholders' Equity \| Towd Point Mortgage Trust \| Asset-backed securities \| Credit Concentration Risk
Securities Available-for-Sale
Amortized Cost	34,308
Fair Value	33,318
Stockholders' Equity \| Student Marketing Association [Member] \| Asset-backed securities \| Credit Concentration Risk
Securities Available-for-Sale
Amortized Cost	25,808
Fair Value	$ 26,119
Minimum \| Stockholders' Equity \| Towd Point Mortgage Trust \| Asset-backed securities \| Credit Concentration Risk
Other disclosures
Credit risk as a percentage of benchmark	10.00%
Minimum \| Stockholders' Equity \| Student Marketing Association [Member] \| Asset-backed securities \| Credit Concentration Risk
Other disclosures
Credit risk as a percentage of benchmark	10.00%