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Schedule of Asset Allocation (Detail) | Dec. 31, 2017 | Mar. 31, 2017
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Supplemental Executive Retirement Plan |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 100.00% |
Actual asset allocations | 100.00% |
Supplemental Executive Retirement Plan | Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 65.00% |
Actual asset allocations | 59.00% |
Supplemental Executive Retirement Plan | Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 35.00% |
Actual asset allocations | 38.00% |
Supplemental Executive Retirement Plan | Cash And Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations | 3.00% |
Supplemental Executive Retirement Plan | Predecessor |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 100.00%
Supplemental Executive Retirement Plan | Predecessor | Equity Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 59.00%
Supplemental Executive Retirement Plan | Predecessor | Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 37.00%
Supplemental Executive Retirement Plan | Predecessor | Cash And Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 4.00%
United States |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 100.00% |
Actual asset allocations | 100.00% |
United States | Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Target asset allocation | 100.00% |
Actual asset allocations | 98.00% |
United States | Cash And Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations | 2.00% |
United States | Predecessor |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 100.00%
United States | Predecessor | Debt Securities |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 98.00%
United States | Predecessor | Cash And Other |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Actual asset allocations |  | 2.00%

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- Definition Percentage of target investment allocation to total plan assets. Includes, but is not limited to, percentage on weighted-average basis if more than one plan. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 55 -Paragraph 17 -URI http://asc.fasb.org/extlink&oid=112275985&loc=d3e4179-114921 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(i) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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