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Consolidated Statements of Changes In Shareholders' Equity (Parenthetical) - $ / shares | 9 Months Ended
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Sep. 30, 2018 | Sep. 30, 2017
Statement of Stockholders' Equity [Abstract] |  |
Cash dividends (in dollars per share) | $ 1.05 | $ 0.90
Common Stock | Class A Common Stock |  |
Stock repurchased during period (in shares) | 125,000 | 0

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