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Summary of Minimum And Maximum Rate of Return of Plan Assets (Detail) - Supplemental Executive Retirement Plan | 9 Months Ended
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Dec. 31, 2017
Minimum | Equity Securities |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 5.00%
Minimum | Debt Securities |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 1.00%
Minimum | Cash and Cash Equivalents |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 0.00%
Maximum | Equity Securities |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 7.00%
Maximum | Debt Securities |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 3.00%
Maximum | Cash and Cash Equivalents |
Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] |
Expected Rate of Return on Plan Assets | 1.00%

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- Definition Schedule of Pension and Other Postretirement Benefits Expected Benefit Payments [Line Items] + References No definition available. + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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