Segment Information - Net Income Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment profit	$ 42,463	$ 46,110	$ 90,730	$ 93,710
Unallocated amounts:
Administrative costs	(5,051)	(4,866)	(11,130)	(11,575)
Investment and other income	2,036	1,760	2,191	3,140
Interest expense	(51)	(647)	(157)	(1,348)
Income before income taxes and losses of unconsolidated affiliate	39,397	42,357	81,634	83,927
Workplace Safety
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment profit	3,463	5,455	11,451	10,612
ID Solutions
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment profit	$ 39,000	$ 40,655	$ 79,279	$ 83,098