Business Segment Information - Reconciliation of Segment Operating Income to Income (Loss) from Operations before Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
LIFO expense	$ 0	$ (28,308)
Employee severance, litigation, and other	(30,021)	(21,066)
Operating income	418,973	399,987
Other loss (income)	324	(123)
Interest expense, net	35,864	36,972
Loss on early retirement of debt	23,766	0
Income before income taxes	359,019	363,138
Operating segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Operating income	488,050	486,195
Segment reconciling items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Gain from antitrust litigation settlements	0	1,395
LIFO expense	0	(28,308)
Acquisition-related intangibles amortization	(39,056)	(38,229)
Employee severance, litigation, and other	$ (30,021)	$ (21,066)