BUSINESS SEGMENTS - Income Before Taxes From Continuing Operations (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
	Dec. 31, 2017	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Segment Reporting Information [Line Items]
Segment operating profit:		$ 24,498	$ 17,429	$ 57,333	$ 52,225
Net interest expense		(15,796)	(12,662)	(48,482)	(38,656)
Unallocated amounts		12,016	10,613	32,993	31,379
Secondary equity offering costs		(1,205)	0	(1,205)	0
Income before taxes from continuing operations	$ 13,715
Income before taxes from continuing operations		9,002	4,547	10,117	13,147
Continuing Operations [Member]
Segment Reporting Information [Line Items]
Special dividend ESOP charges		(3,220)	0	(3,220)	0
Secondary equity offering costs		(1,205)		(1,205)
Postretirement Life Insurance [Member] | Continuing Operations [Member]
Segment Reporting Information [Line Items]
Segment operating profit from continuing operations		44,837	27,822	103,848	83,182
Net interest expense		(15,796)	(12,662)	(48,482)	(38,656)
Unallocated amounts		12,016	10,613	32,993	31,379
Acquisition costs		(3,598)	0	(5,217)	0
Income before taxes from continuing operations		0	0	(2,614)	0
Income before taxes from continuing operations		9,002	4,547	10,117	13,147
Postretirement Life Insurance [Member] | Continuing Operations [Member] | Home And Building Products [Member]
Segment Reporting Information [Line Items]
Segment operating profit:		38,753	23,708	94,982	64,661
Postretirement Life Insurance [Member] | Continuing Operations [Member] | Telephonics [Member]
Segment Reporting Information [Line Items]
Segment operating profit:		$ 6,084	$ 4,114	$ 8,866	$ 18,521