Consolidated Statements of Comprehensive Income (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Tax on (loss) gain on derivative instruments	$ 12,016	$ 2,911	$ 0
Tax on reclassifications of net losses (gains) on derivative instruments	(1,112)	(1,109)	(1,112)
Tax on benefit plans	2,267	2,469	1,002
Tax on reclassification of benefits plans actuarial losses and prior service cost	$ (454)	$ (367)	$ (274)