Delinquencies as a percentage of loans in repayment.

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Loan status forbearance recorded investment.

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Loan status in school grace and deferment recorded investment.

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Loans in forbearance as a percentage of loans in repayment and forbearance.

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Total loans in repayment.

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Loans in repayment and percentage of each status.

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Loans in repayment current in percentage.

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Total loans in repayment, in percentage.

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Percentage of loans in repayment.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage of financing receivable balance that is past due.

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Financing receivables that are current.

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Recorded Investment in financing receivables that are past due at the balance sheet date.

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Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

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Amount, before allowance and fees, of loans and leases receivable. Excludes loans and leases covered under loss sharing agreements.

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Amount before allowance of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans and leases covered under loss sharing agreements.

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Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums and discounts from face amounts, of loans and leases held in portfolio, including but not limited to, commercial and consumer loans. Excludes loans and leases covered under loss sharing agreements and loans held for sale.

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Amount of deferred fees paid by borrowers and unamortized costs incurred to originate loans and leases, unamortized loan commitments and loan syndication fees, and premiums over or discounts from face amounts of loans that are being amortized into income as an adjustment to yield. Excludes amounts for loans and leases covered under loss sharing agreements.

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Allowance for Loan Losses - Age Analysis of Past Due Loans Delinquencies (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Loans in repayment and percentage of each status:
Private Education Loans allowance for losses	$ (358,325)	$ (341,121)	$ (272,123)	$ (251,475)
Loans held for investment, net	23,498,386	22,270,919
Private Education Loans
Loans in repayment and percentage of each status:
Total Private Education Loans, gross	21,791,622	20,504,465
Private Education Loans deferred origination costs	70,858	68,321
Private Education Loans allowance for losses	(285,946)	(277,943)
Loans held for investment, net	21,576,534	20,294,843
Private Education Loans \| Consumer Portfolio Segment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans in-school/grace/deferment	5,870,853	5,260,445
Loans in forbearance	610,209	577,164
Loans in repayment and percentage of each status:
Loans current	$ 14,927,591	$ 14,289,705
Loans current (as a percentage)	97.50%	97.40%
Total TDR loans in repayment	$ 15,310,560	$ 14,666,856
Total TDR loans in repayment (as a percentage)	100.00%	100.00%
Total Private Education Loans, gross	$ 21,791,622	$ 20,504,465
Private Education Loans deferred origination costs	70,858	68,321
Total Private Education Loans, gross	21,862,480	20,572,786
Private Education Loans allowance for losses	(285,946)	(277,943)
Loans held for investment, net	$ 21,576,534	$ 20,294,843
Percentage of Private Education Loans in repayment	70.30%	71.50%
Delinquencies as a percentage of Private Education Loans in repayment	2.50%	2.60%
Loans in forbearance as a percentage of Private Education Loans in repayment and forbearance	3.80%	3.80%
Private Education Loans \| Consumer Portfolio Segment \| Loans delinquent 31-60 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 216,295	$ 231,216
Loans delinquent (as a percentage)	1.40%	1.60%
Private Education Loans \| Consumer Portfolio Segment \| Loans delinquent 61-90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 104,199	$ 95,105
Loans delinquent (as a percentage)	0.70%	0.70%
Private Education Loans \| Consumer Portfolio Segment \| Loans delinquent, greater than 90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 62,475	$ 50,830
Loans delinquent (as a percentage)	0.40%	0.30%
Personal Loans
Loans in repayment and percentage of each status:
Total Private Education Loans, gross	$ 1,162,874	$ 1,190,091
Private Education Loans deferred origination costs	394	297
Private Education Loans allowance for losses	(70,619)	(62,201)
Loans held for investment, net	1,092,649	1,128,187
Personal Loans \| Consumer Portfolio Segment
Loans in repayment and percentage of each status:
Loans current	$ 1,141,664	$ 1,172,776
Loans current (as a percentage)	98.20%	98.50%
Total TDR loans in repayment	$ 1,162,874	$ 1,190,091
Total TDR loans in repayment (as a percentage)	100.00%	100.00%
Total Private Education Loans, gross	$ 1,162,874	$ 1,190,091
Private Education Loans deferred origination costs	394	297
Total Private Education Loans, gross	1,163,268	1,190,388
Private Education Loans allowance for losses	(70,619)	(62,201)
Loans held for investment, net	$ 1,092,649	$ 1,128,187
Delinquencies as a percentage of Private Education Loans in repayment	1.80%	1.50%
Personal Loans \| Consumer Portfolio Segment \| Loans delinquent 31-60 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 9,224	$ 6,722
Loans delinquent (as a percentage)	0.80%	0.60%
Personal Loans \| Consumer Portfolio Segment \| Loans delinquent 61-90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 5,991	$ 5,416
Loans delinquent (as a percentage)	0.50%	0.50%
Personal Loans \| Consumer Portfolio Segment \| Loans delinquent, greater than 90 days
Loans in repayment and percentage of each status:
Loans delinquent	$ 5,995	$ 5,177
Loans delinquent (as a percentage)	0.50%	0.40%