Selected Quarterly Financial Data (Unaudited) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2018
Quarterly Financial Information Disclosure [Abstract]
Total revenue	$ 686,748,000	$ 533,112,000	$ 489,413,000	$ 417,804,000	$ 781,701,000	$ 482,738,000	$ 421,260,000	$ 402,040,000
Gross profit	116,600,000	89,058,000	78,845,000	63,137,000	116,297,000	71,764,000	(82,680,000)	60,655,000	$ 347,640,000	$ 166,036,000	$ 345,015,000
Operating income (loss)	35,586,000	23,151,000	16,424,000	3,946,000	36,005,000	9,543,000	(138,950,000)	3,506,000	79,107,000	(89,896,000)	81,548,000
Net income (loss) from continuing operations	$ 24,627,000	$ 15,270,000	$ 10,615,000	$ 2,804,000	$ 2,464,000	$ 11,625,000	$ (100,832,000)	$ 7,322,000	$ 53,316,000	$ (79,421,000)	$ (45,046,000)
Basic EPS from continuing operations (in dollars per share)	$ 0.83	$ 0.51	$ 0.36	$ 0.09	$ 0.08	$ 0.38	$ (3.28)	$ 0.23	$ 1.80	$ (2.59)	$ (1.40)
Diluted EPS from continuing operations (in dollars per share)	$ 0.82	$ 0.51	$ 0.35	$ 0.09	$ 0.08	$ 0.38	$ (3.28)	$ 0.23	$ 1.78	$ (2.59)	$ (1.40)
Production Related Impairments or Charges [Abstract]
Inventory impairments and abandonments	$ 637,000	$ 2,266,000	$ 0	$ 0	$ 0	$ 0	$ 147,611,000	$ 1,007,000	$ 2,903,000	$ 148,618,000	$ 6,499,000
Gain (Loss) on Extinguishment of Debt [Abstract]
Loss on extinguishment of debt, net	$ 0	$ 0	$ 0	$ 0	$ (25,494,000)	$ 358,000	$ 216,000	$ 0	$ 0	$ (24,920,000)	$ (27,839,000)