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CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) (Parenthetical) - USD ($) $ in Thousands | Sep. 30, 2020 | Dec. 31, 2019
--- | --- | ---
Assets: |  |
Available-for-sale investment securities, cost | $ 3,068,406 | $ 3,011,551
Equity and other securities, cost | $ 46,419 | $ 42,965
Shareholders' equity: |  |
Preferred stock, par value (in dollars per share) | $ 1.00 | $ 1.00
Preferred stock, shares authorized (in shares) | 500,000 | 500,000
Preferred stock, shares issued (in shares) | 0 | 0
Common stock, par value (in dollars per share) | $ 1.00 | $ 1.00
Common stock, shares authorized (in shares) | 75,000,000 | 75,000,000
Common stock, shares issued (in shares) | 53,697,919 | 51,974,726
Treasury stock, shares at cost (in shares) | 160,326 | 180,803
Shares held by deferred compensation arrangements (in shares) | 160,311 | 179,548

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