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Employee Benefit Plans - Summary of Weighted-Average Assumptions for Disclosure (Detail) | Dec. 31, 2018 | Dec. 31, 2017
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Pension Plan [Member] |  |
Weighted-average assumptions for Disclosure |  |
Discount rate |  | 1.80%
Supplemental Employee Retirement Plan [Member] |  |
Weighted-average assumptions for Disclosure |  |
Discount rate | 4.00% | 3.35%
Postretirement Benefits [Member] |  |
Weighted-average assumptions for Disclosure |  |
Discount rate |  | 3.75%

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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation 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)(1) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

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- References No definition available. + Details
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- Details
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- Details
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Namespace Prefix: |
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- Details
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Balance Type: |
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