Consolidated Statements of Earnings and Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2018	Mar. 31, 2017
Income Statement [Abstract]
Net sales	$ 390,183	$ 364,599	$ 753,274	$ 703,970
Cost of sales	284,448	269,844	553,115	519,758
Gross profit	105,735	94,755	200,159	184,212
Selling, general and administrative expenses	72,539	62,557	142,391	125,758
Income from operations	33,196	32,198	57,768	58,454
Interest expense, net	(11,965)	(8,842)	(23,803)	(19,915)
Other (expense) income, net	(108)	(255)	152	33
Income before provision for income taxes	21,123	23,101	34,117	38,572
Provision for income taxes	(6,123)	(5,659)	(19,491)	(8,023)
Net income	15,000	17,442	14,626	30,549
Other comprehensive income (loss), net of income taxes	2,850	5,575	4,115	(5,682)
Comprehensive income	$ 17,850	$ 23,017	$ 18,741	$ 24,867
Net income per share:
Basic net income per share (in dollars per share)	$ 0.15	$ 0.18	$ 0.15	$ 0.31
Diluted net income per share (in dollars per share)	$ 0.15	$ 0.18	$ 0.15	$ 0.31
Weighted average shares outstanding:
Basic weighted average shares outstanding (in shares)	99,136,015	98,709,557	99,116,250	98,512,601
Dilutive weighted average shares outstanding (in shares)	99,519,925	99,017,986	99,441,385	98,900,437