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Fair Value of Financial Instruments - Carrying Value and Fair Value of Long-Term Debt (Parenthetical) (Detail) | Sep. 30, 2018 | Dec. 31, 2017
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2.40% Term Loan, Due Jun. 2022 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Percent on aggregate principal amount of outstanding | 2.40% | 2.40%
2.05% Term Loan, Due Mar. 2023 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Percent on aggregate principal amount of outstanding | 2.05% | 2.05%
1.30% Term Loan, Due Jun. 2023 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Percent on aggregate principal amount of outstanding | 1.30% | 1.30%
1.55% Term Loan, Due Sep. 2025 [Member] |  |
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] |  |
Percent on aggregate principal amount of outstanding | 1.55% | 1.55%

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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + 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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- Details
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- Details
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- Details
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- Details
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