CONSOLIDATED STATEMENTS OF CONDITION (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Assets:
Available-for-sale investment securities, Pledged Amount	$ 436,813	$ 485,414
Available-for-sale investment securities, cost	6,191,809	4,980,102
Equity and other securities, cost	$ 43,494	$ 43,917
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)	54,163,637	54,092,421
Treasury stock, shares at cost (in shares)	250,275	214,374
Shares held by deferred compensation arrangements (in shares)	132,759	146,860