Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 23,351	$ 38,839
Other comprehensive income:
Net gains on derivative instruments (net of tax of $(1,332) and $0, respectively)	1,877	0
Reclassifications of net losses on derivative instruments (net of tax of $(276) and $(278), respectively)	390	391
Benefit plans reclassifications of actuarial losses and prior service costs (net of tax of $(113) and $(91), respectively)	160	131
Other comprehensive income	2,427	522
Comprehensive income	$ 25,778	$ 39,361