The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Schedule I - Condensed Financial Information - Condensed Statements of Operations (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Sep. 30, 2019	Jun. 28, 2019	Mar. 29, 2019	Dec. 28, 2018	Sep. 30, 2018	Jun. 29, 2018	Mar. 30, 2018	Dec. 29, 2017	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2017
Condensed Income Statements, Captions [Line Items]
Net income	$ 45,997	$ 36,550	$ 29,555	$ 26,949	$ 32,699	$ 34,199	$ 42,558	$ 27,189	$ 139,051	$ 136,645	$ 84,639
Other comprehensive (loss) income of subsidiary, net of tax									(22,927)	1,544	7,968
Comprehensive income									116,124	138,189	92,607
Atkore International Group Inc.
Condensed Income Statements, Captions [Line Items]
Net income									139,051	136,645	84,639
Other comprehensive (loss) income of subsidiary, net of tax									(22,927)
Comprehensive income									$ 116,124	$ 138,189	$ 92,607