Low Income Housing Partnerships (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Investments in Affordable Housing Projects [Abstract]
Investment In affordable housing limited partnerships	$ 89,700	$ 82,600
Obligations related to investments in affordable housing limited partnerships	$ 44,500	40,000
Affordable housing tax credits commitment, year to be paid	2022
Proportional amortization expense, amount	$ 7,900	6,800	$ 7,000
Affordable housing tax credits, amount	9,800	8,600	7,500
Net income tax benefit, low income housing partnerships	1,900	1,800	500
Impairment losses from the forfeiture or ineligibility of tax credits or other circumstances, amount	$ 0	$ 0	$ 0