Condensed Consolidated Statements of Stockholders' Equity (Unaudited) (Parentheticals) - USD ($) $ in Thousands	3 Months Ended
Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020
Common Class A [Member]
Dividends declared (in dollars per share)	$ 0.06	$ 0.06	$ 0.06	$ 0.06
Common Class B [Member]
Dividends declared (in dollars per share)	$ 0.07	$ 0.07	$ 0.07	$ 0.07
Foreign currency translation adjustment, tax expense	$ (333)	$ 9	$ (3)	$ (27)
Change in unfunded SERP liability, tax	$ (28)	$ (28)	$ (20)	$ (20)

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

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Amount of tax expense (benefit) for (increase) decrease in value of benefit obligation for change in actuarial assumptions and increase (decrease) in value of plan assets from experience different from that assumed of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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Amount of tax expense (benefit), after reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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