Consolidated Condensed Statements of Shareholders' Equity (Parenthetical) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement Of Stockholders Equity [Abstract]
Tax effect on employee benefit funded status adjustment	$ 141	$ 1,894	$ 137	$ 1,914
Cash dividends (in dollars per share)	$ 0.15	$ 0.13	$ 0.30	$ 0.26
Issuance of treasury stock (in shares)	19	9	28	30

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income for defined benefit plan, attributable to parent.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
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