Segment Information (Detail) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Segment Reporting Information [Line Items]
Total consolidated net sales		$ 113,851	$ 79,071	$ 224,515	$ 155,566
Total consolidated depreciation and amortization				14,695	7,048
Total consolidated operating income		21,730	9,040	41,810	17,720
Total other (expense) income, net		(4,574)	(457)	(16,175)	(404)
Income before income taxes		17,156	8,583	25,635	17,316
Operating Segments
Segment Reporting Information [Line Items]
Total consolidated net sales		113,851	79,071	224,515	155,566
Total consolidated depreciation and amortization		7,586	3,496	14,695	7,048
Total consolidated operating income	[1]	21,730	9,040	41,810	17,720
Total other (expense) income, net		(4,574)	(457)	(16,175)	(404)
Income before income taxes		17,156	8,583	25,635	17,316
Operating Segments | Electronic Chemicals
Segment Reporting Information [Line Items]
Total consolidated net sales		73,924	69,766	147,732	136,688
Total consolidated depreciation and amortization		2,760	2,793	5,554	5,645
Total consolidated operating income	[1]	12,730	9,583	23,988	17,644
Operating Segments | Performance Materials
Segment Reporting Information [Line Items]
Total consolidated net sales		39,927	9,305	76,783	18,878
Total consolidated depreciation and amortization		4,287	285	8,168	572
Total consolidated operating income	[1]	12,810	3,023	24,394	6,704
Other Activities
Segment Reporting Information [Line Items]
Total consolidated depreciation and amortization		539	418	973	831
Total consolidated operating income	[1]	$ (3,810)	$ (3,566)	$ (6,572)	$ (6,628)

[1] Segment income from operations includes allocated corporate overhead expenses, but excludes restructuring and realignment charges, which are included in other activities.