Segment Information (Detail 2) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Mar. 31, 2016	Mar. 31, 2015
Revenue recognition
Increase (decrease) in operating income	$ (9,086)	$ 23,206	$ (17,163)	$ 30,385
Increase (decrease) in net income	$ 10,144	$ (11,011)	$ 4,730	$ (5,849)
Increase (decrease) in net income per common share (in dollars per share)	$ 0.38	$ (0.41)	$ 0.18	$ (0.22)
Unallocated corporate expenses and other
Revenue recognition
Increase (decrease) in operating income	$ (12,000)	$ (7,200)	$ (20,500)	$ (9,400)
Expense related to the development of ERP system	6,900	300	12,200	1,900
Change in estimated total costs | Adjustment
Revenue recognition
Increase (decrease) in operating income	(300)	0	(2,400)	(13,500)
Increase (decrease) in net income	$ (200)	$ 0	$ (1,400)	$ (8,300)
Increase (decrease) in net income per common share (in dollars per share)	$ (0.01)		$ (0.05)	$ (0.31)