Condensed Consolidated Balance Sheets (unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2016	Sep. 30, 2015	Mar. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowances for doubtful accounts	$ 12,858	$ 12,257	$ 18,141
Property, plant and equipment, accumulated depreciation and amortization	$ 1,435,097	$ 1,369,733	$ 1,302,098
Common unitholders, units issued	92,922,445	92,889,980	92,888,829