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CONSOLIDATED STATEMENTS OF CONDITION (Unaudited) (Parenthetical) - USD ($) $ in Thousands | Jun. 30, 2018 | Dec. 31, 2017
--- | --- | ---
Assets: |  |
Available-for-sale investment securities, cost | $ 2,972,889 | $ 3,007,148
Equity and other securities, cost | $ 43,155 | $ 50,291
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) | 51,511,992 | 51,263,841
Treasury stock, shares at cost (in shares) | 426,118 | 567,764
Shares held by deferred compensation arrangements (in shares) | 205,017 | 237,494

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