Consolidated Statements of Condition (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Held-to-Maturity: Fair Value	$ 3,288,668	$ 3,062,882
Common Stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common Stock, authorized (in shares)	500,000,000	500,000,000
Common Stock, issued (in shares)	58,248,690	58,166,910
Common Stock, outstanding (in shares)	40,060,675	40,039,695
Treasury Stock (in shares)	18,188,015	18,127,215