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Employee Benefit Plans (Pension Benefit Plan) - Additional Information (Detail) - USD ($) $ in Millions | 12 Months Ended |
--- | --- | ---
Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |
Accumulated benefit obligation | $ 37.2 | $ 32.9
Estimated amortization from accumulated other comprehensive income into net periodic pension cost in 2019 | 0.7 |
Expected employer contribution to pension plan in 2019 | $ 1.1 |
Bond Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of target allocation ranges by asset class | 50.00% |
Equity Funds [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of target allocation ranges by asset class | 40.00% |
Cash, Real Estate, and Managed Futures [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Percentage of target allocation ranges by asset class | 10.00% |
Minimum [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
Threshold for unamortized gain losses | 10.00% |

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- Definition Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level. + 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 (e) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount included in accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan expected to be recognized in net periodic benefit (cost) credit for fiscal year following most recent annual statement of financial position. + 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 (s) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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- Definition Amount of contributions expected to be received by defined benefit plan from employer in next fiscal year following latest fiscal year. + 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 (g) -URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920 + Details
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