Consolidated Statements of Stockholders' Equity (Parenthetical) - USD ($)	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash dividend declared	$ 0.68	$ 0.66	$ 0.60
Retained Earnings [Member]
Cash dividend declared	$ 0.68	$ 0.66	$ 0.60
Accumulated Other Comprehensive Income (Loss) [Member]
Minimum Pension adjustment, tax	$ 100,000	$ 1,118,000	$ 111,000
Tax expense for Derivative Financial Instrument	$ 3,300,000	$ 101,000	$ 52,000

Other comprehensive income minimum pension liability net adjustments tax.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- Definition

Amount, before reclassification, of tax expense (benefit) for gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 12
-URI http://asc.fasb.org/extlink&oid=114867106&loc=d3e640-108580

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