Segment Information - Revenues and Long-Lived Assets by Geographic Information (Details) - USD ($) $ in Thousands	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
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 166,860	$ 210,233	$ 223,283	$ 222,435	$ 214,339	$ 202,465	$ 214,730	$ 215,695	$ 822,811	$ 847,229	$ 812,156
Total long-lived assets	56,986				67,357				56,986	67,357
Lana
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									34	0	0
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									638,844	650,413	635,780
Total long-lived assets	36,361				43,274				36,361	43,274
Mexico
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									131,965	138,897	122,702
Total long-lived assets	15,141				18,566				15,141	18,566
Other Latin America
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									48,146	52,288	45,554
Total long-lived assets	5,484				5,432				5,484	5,432
Canada and other
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									3,822	5,631	$ 8,120
Total long-lived assets	$ 0				$ 85				$ 0	$ 85