Financial Instruments (Interest Rate Swaps) - Additional Information (Detail) - Interest Rate Swap [Member]	12 Months Ended
Dec. 31, 2017 USD ($) Interest_Rate_Swaps	Dec. 31, 2016 USD ($)
Schedule Of Available For Sale Securities [Line Items]
Fair value hedging instruments	$ 0	$ 0
Interest rate swap, description of interest received	interest that varies with the one-month LIBOR
Derivative, Type of Interest Rate Paid on Swap	fixed
November 2018 [Member]
Schedule Of Available For Sale Securities [Line Items]
Notional value	$ 15,000,000
Interest rate swap, fixed interest rate	1.155%
October 2020 [Member]
Schedule Of Available For Sale Securities [Line Items]
Notional value	$ 25,000,000
Interest rate swap, fixed interest rate	1.30%
February 2021 [Member]
Schedule Of Available For Sale Securities [Line Items]
Notional value	$ 10,000,000
Interest rate swap, fixed interest rate	1.12%
May 2022 [Member]
Schedule Of Available For Sale Securities [Line Items]
Notional value	$ 20,000,000
Interest rate swap, fixed interest rate	1.77%
Second Quarter 2017 [Member]
Schedule Of Available For Sale Securities [Line Items]
Notional value	$ 20,000,000
Interest rate swap, term	5 years
Fourth Quarter 2017 [Member]
Schedule Of Available For Sale Securities [Line Items]
Number of interest rate swaps \| Interest_Rate_Swaps	1
Notional value	$ 10,000,000

Derivative Floating Interest Rate Description

No definition available.

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- Definition

When the derivative or group of derivatives presented is a swap, the type of interest rate (fixed, variable, stepped, etc.) paid on the swap.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column A
-Footnote 1

+ Details

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- Definition

Fixed interest rate related to the interest rate derivative.

+ References

No definition available.

+ Details

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- Definition

Nominal or face amount used to calculate payments on the derivative liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

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- Definition

Period the derivative contract is outstanding, 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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- Definition

Net fair value of all derivative instruments designated as fair value hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

Number of interest rate derivative instruments held by the entity at the reporting date.

+ References

+ 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.

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