Summary of Significant Accounting Policies and Practices - Allowance for Loan Losses (Details) - USD ($)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Allowance for Credit Losses [Line Items]
Threshold period past due for financing receivable to be placed on nonaccrual status	90 days
Threshold period past due for write-off of financing receivable	120 days
Impaired loans	$ 0	$ 0
Loans disbursed on or after July 1, 2006 [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Percent of principal and interest federally guaranteed	97.00%
Loans disbursed between October 1, 1993 and July 1, 2006 [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Percent of principal and interest federally guaranteed	98.00%

Percent of Principal and Interest Federally Guaranteed

No definition available.

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- Definition

Threshold Period Past Due For Financing Receivable to be Placed on Nonaccrual Status

+ References

No definition available.

+ Details

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- Definition

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.

+ References

No definition available.

+ Details

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- Definition

Amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 14A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953550-111524

+ Details

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- Definition

Threshold period past due for financing receivable to write off as uncollectible, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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- Details

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- Details

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