Condensed Consolidating Information - Consolidating cash flow statement (Details) - USD ($) $ in Thousands	6 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Condensed Cash Flow Statements
Net cash provided by (used in) operating activities	$ 45,300	$ 46,500
Investing activities:
Capital expenditures	(15,000)	(8,300)
Proceeds from sales of property, plant, and equipment	13,300	0
Acquisition of businesses, net of cash acquired	(1,503,100)	(26,200)
Proceeds from divestiture, net of cash divested	222,400	0
Other, net	0	100
Net cash used in investing activities	(1,282,400)	(34,400)
Financing activities:
Proceeds from issuance of long-term debt	725,000	0
Repayments on long-term debt	(9,100)	0
Proceeds from revolving credit facilities	1,082,800	342,000
Repayments on revolving credit facilities	(544,700)	(323,800)
Payment of deferred financing costs	(7,000)	0
Payment of dividends on common stock	(31,700)	(26,200)
Proceeds from stock option exercises	200	1,400
Payments for employee taxes on net settlement equity awards	(1,800)	(4,200)
Other, net	(1,100)	(500)
Net cash provided by (used in) financing activities	1,212,600	(11,300)
Effect of exchange rates on cash and cash equivalents	(500)	2,100
Net cash flows	(25,000)	2,900
At beginning of period	399,400	56,500
At end of period	374,400	59,400
Reportable legal entities | Parent
Condensed Cash Flow Statements
Net cash provided by (used in) operating activities	2,000	(4,700)
Investing activities:
Capital expenditures	(700)	(400)
Proceeds from sales of property, plant, and equipment		0
Acquisition of businesses, net of cash acquired	(1,503,100)
Proceeds from divestiture, net of cash divested	222,400
Other, net	0	0
Net cash used in investing activities	(1,281,400)	(400)
Financing activities:
Proceeds from issuance of long-term debt	725,000
Repayments on long-term debt	(9,100)	0
Proceeds from revolving credit facilities	804,000	164,000
Repayments on revolving credit facilities	(338,000)	(130,800)
Payment of deferred financing costs	(7,000)
Payment of dividends on common stock	(31,700)	(26,200)
Proceeds from stock option exercises	200	1,400
Payments for employee taxes on net settlement equity awards	(1,800)	(4,200)
Other, net	0	0
Net cash provided by (used in) financing activities	1,141,600	4,200
Net cash flows	(137,800)	(900)
At beginning of period	283,100	1,100
At end of period	145,300	200
Reportable legal entities | Guarantors
Condensed Cash Flow Statements
Net cash provided by (used in) operating activities	103,200	103,000
Investing activities:
Capital expenditures	(5,300)	(3,600)
Proceeds from sales of property, plant, and equipment	100	0
Other, net	0	100
Net cash used in investing activities	(5,200)	(3,500)
Financing activities:
Payment of Intercompany Dividends	(96,100)	(100,000)
Net cash provided by (used in) financing activities	(96,100)	(100,000)
Net cash flows	1,900	(500)
At beginning of period	9,600	5,800
At end of period	11,500	5,300
Reportable legal entities | Non-Guarantors
Condensed Cash Flow Statements
Net cash provided by (used in) operating activities	42,600	54,600
Investing activities:
Capital expenditures	(9,000)	(4,300)
Proceeds from sales of property, plant, and equipment	13,200	0
Acquisition of businesses, net of cash acquired		(26,200)
Proceeds from divestiture, net of cash divested		0
Other, net	0	0
Net cash used in investing activities	4,200	(30,500)
Financing activities:
Proceeds from revolving credit facilities	278,800	178,000
Repayments on revolving credit facilities	(206,700)	(193,000)
Payment of Intercompany Dividends	(6,400)	(6,400)
Other, net	(1,100)	(500)
Net cash provided by (used in) financing activities	64,600	(21,900)
Effect of exchange rates on cash and cash equivalents	(500)	2,100
Net cash flows	110,900	4,300
At beginning of period	106,700	49,600
At end of period	217,600	53,900
Eliminations
Condensed Cash Flow Statements
Net cash provided by (used in) operating activities	(102,500)	(106,400)
Financing activities:
Payment of Intercompany Dividends	102,500	106,400
Net cash provided by (used in) financing activities	$ 102,500	$ 106,400