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Retirement Plans - Defined Benefit Plan, Fair Value of Plan Assets, Unobservable Input Reconciliation (Detail) - Bank And Insurance Investment Contracts [Member] - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Fair value of defined benefit plan assets, beginning balance	$ 51,963	$ 45,093
Net purchases (sales) and appreciation (depreciation) of defined benefit plan assets	4,755	6,870
Fair value of defined benefit plan assets, ending balance	$ 56,718	$ 51,963

X

- Definition

Amount, measured using unobservable inputs, of increase (decrease) in plan assets of defined benefit plan.

+ References

No definition available.

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- Definition

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.

+ References

No definition available.

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- Definition

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 20
-Section 50
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