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.

No definition available.

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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

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- Definition

Percentage of actual 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/2009/role/commonPracticeRef
-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

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Schedule of Asset Allocation (Detail)	Dec. 31, 2017	Mar. 31, 2017
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%