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Stock Plans - Additional Information (Details) | 3 Months Ended | 6 Months Ended
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Mar. 31, 2018 | Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percentage of target award based on achieving specified performance targets | 93.60% |
Minimum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percentage of target award based on achieving targeted performance conditions | 0.00% |
Maximum |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Percentage of target award based on achieving targeted performance conditions | 200.00% |
Performance Shares |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Fair value assumptions, average closing price used to calculate expected dividend rate, period (years) |  | 1 year
Stock beta, daily price data period (years) |  | 10 years
Performance Shares |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |
Award vesting period (in years) | 3 years |

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- Definition Percentage of target award based on achieving a targeted return on net assets based on which final number of shares to be issued for performance stock units. + References No definition available. + Details
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- Definition Percentage of target award based on achieving a targeted total shareholder return based on which final number of shares to be issued for performance stock units. + References No definition available. + Details
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- Definition Share-based Compensation Arrangement by Share-base Payment Award, Fair Value Assumptions, Average Closing Price Used to Calculate Expected Dividend Rate, Period + References No definition available. + 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://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a)(1) -URI http://asc.fasb.org/extlink&oid=96867065&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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