Consolidated Statements Of Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Preferred stock, no par value (in usd per share)	$ 0	$ 0
Preferred stock, 20,000,000 shares authorized	20,000,000	20,000,000
Common stock, no par value (in usd per share)	$ 0	$ 0
Common stock, stated value (in usd per share)	$ 1.00	$ 1.00
Common stock shares authorized (in shares)	100,000,000	100,000,000
Shares issued	56,068,220	51,978,289
Treasury stock, shares	103,013	97,749
Held-to-maturity securities, fair value	$ 812,516	$ 607,602
Series C preferred stock
Preferred stock, liquidation value per share	$ 1,000	$ 1,000
Shares issued	0	126,257
Shares outstanding	0	126,257
Series D preferred stock
Preferred stock, liquidation value per share	$ 25	$ 25
Shares issued	5,000,000	5,000,000
Shares outstanding	5,000,000	5,000,000