Commitments and Contingencies (Details 2) - USD ($) $ in Thousands	12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2013
Commitments and Contingencies
Actual purchases made under contracts with minimum requirements	$ 32,700	$ 20,300	$ 14,900
2016	18,123
2017	16,499
2018	13,930
2019	13,539
2020	13,811
Thereafter	62,096
Future purchase requirements, total	137,998
Increase in future purchase requirements due to contract extensions subsequent to end of year	$ 43,000