Consolidated Statements of Stockholders' Equity (Parenthetical) - $ / shares	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Dividend reinvestment plan, shares	5,694	6,298
Stock purchase and compensation plans, shares	371,628	349,255
Dividends to stockholders, per share	$ 0.20	$ 0.18
Acquisition of treasury stock, shares	102,971	103,170
Preferred stock, par value per share	$ 0	$ 0
Preferred stock, shares authorized	5,000,000	5,000,000
Preferred stock, shares issued	0	0
Series A Preferred Stock [Member]
Preferred stock, par value per share	$ 0	$ 0
Preferred stock, shares authorized	300,000	300,000

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

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