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Derivative Instruments - Additional Information (Detail) - USD ($) | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015
Derivative [Line Items] |  |  |
Period of LIBOR interest rate | 30 days |  |
Effective portion of gain/loss on derivatives included as a component of other comprehensive income, net of taxes | $ 11,000 | $ (151,000) | $ (372,000)
Other Assets [Member] |  |  |
Derivative [Line Items] |  |  |
Fair values of interest rate corridor instrument | 509,000 | 490,000 |
Interest Rate Corridor [Member] |  |  |
Derivative [Line Items] |  |  |
Notional amount of derivative instrument | $ 66,667 |  |
Description of interest rate risk hedge at several thresholds | The University pays variable interest monthly based on the 30-day LIBOR rates until that index reaches 1.5%. If 30-dayLIBOR is equal to 1.5% through 3.0%, the University pays 1.5%. If 30-day LIBOR exceeds 3.0%, the University pays actual 30-day LIBOR less 1.5%. |  |
Interest Rate Corridor [Member] | LIBOR [Member] |  |  |
Derivative [Line Items] |  |  |
Maximum percentage of variable interest rates based on LIBOR | 1.50% |  |
Percentage of amount paid by University | 1.50% |  |
Percentage deducted from LIBOR for actual payment | 1.50% |  |
Interest Rate Corridor [Member] | LIBOR [Member] | Minimum [Member] |  |  |
Derivative [Line Items] |  |  |
Percentage of LIBOR | 1.50% |  |
Interest Rate Corridor [Member] | LIBOR [Member] | Maximum [Member] |  |  |
Derivative [Line Items] |  |  |
Percentage of LIBOR | 3.00% |  |
Cash Flow Hedging [Member] |  |  |
Derivative [Line Items] |  |  |
Effective portion of gain/loss on derivatives included as a component of other comprehensive income, net of taxes | $ 17,000 | $ 245,000 | $ 602,000

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