CONSOLIDATED STATEMENTS OF FINANCIAL CONDITION (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Sep. 30, 2019
Statement of Financial Position [Abstract]
Allowance for credit losses on loans	$ 165,349	$ 131,534
Goodwill	$ 302,707	$ 301,368
Common stock, par value (in dollars per share)	$ 1.00	$ 1.00
Common stock, shares authorized (in shares)	300,000,000	300,000,000
Common stock, shares issued (in shares)	135,743,737	135,539,806
Common stock, shares outstanding (in shares)	75,706,026	78,841,463
Treasury stock, shares (in shares)	60,037,711	56,698,343