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Stock Plans - Additional Information (Detail) - Performance-based stock unit - shares | 1 Months Ended | 6 Months Ended | 12 Months Ended |
--- | --- | --- | --- | ---
May 31, 2018 | Jul. 31, 2017 | May 31, 2017 | Jun. 30, 2018 | Dec. 31, 2016 | Dec. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Other than options, granted | 81,300 | 47,900 | 98,500 |  | 289,900 |
Performance period (years) |  |  |  | 3 years |  |
Net debt to EBITDA ratio |  |  |  |  | 450.00% |
Minimum |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Common stock issuable |  |  |  | 27,000 |  | 106,000
Other than options, shares expected to vest |  |  |  |  | 54,900 |
Maximum |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |
Common stock issuable |  |  |  | 161,800 |  | 227,200
Other than options, shares expected to vest |  |  |  |  | 274,800 |

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- Definition Aggregate number of common shares reserved for future issuance. + 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 210.5-02.29) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + Details
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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901 + 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 Net debt to EBITDA ratio. + References No definition available. + Details
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- Definition Share based compensation arrangement by share based payment award equity instruments other than options expected to vest. + References No definition available. + Details
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