Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2012
Comprehensive Income (Loss), Net of Tax, Attributable to Parent [Abstract]
Tax on (loss) gain on derivative instruments	$ 0	$ 10,746	$ (4,783)
Tax on reclassifications of net losses (gains) on derivative instruments	(1,112)	(334)	(766)
Tax on benefit plans	1,002	(3,325)	1,948
Tax on reclassification of benefits plans actuarial losses and prior service cost	$ (274)	$ (555)	$ (333)