Impact of Restatement to Balance Sheets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Current assets:
Cash and cash equivalents	$ 15,092	$ 17,077	$ 19,307	$ 12,794	$ 10,262	$ 22,314	$ 33,357
Short-term investments	36,137	36,461	28,862	24,739	27,491	18,112
Trade accounts receivable, net	9,435	8,327	16,709	13,819	15,392	12,693
Financing receivables, net	3,055	2,614	1,890	1,678	1,533	2,004
Income tax receivable	273	473	483	13,290	13,290	17,369
Inventories	20,752	22,382	22,655	24,676	30,844	32,422
Prepaid expenses and other current assets	1,623	1,854	1,827	1,855	1,826	1,295
Total current assets	86,367	89,188	91,733	92,851	100,638	106,209
Rental equipment, net	16,462	20,551	24,485	26,821	30,973	46,036
Property, plant and equipment, net	37,399	43,432	44,484	43,477	44,732	48,709
Non-current inventories	55,935	65,642	69,448	77,089	73,696	92,378
Deferred income tax assets, net	259	267	247	179	216	4,554
Non-current financing receivables, net	8,195	588	427	1,385	1,817	1,516
Prepaid income taxes	450	1,464	1,843	2,227	2,620	4,095
Other assets	629	641	80	80	80	95
Total assets	205,696	221,773	232,747	244,109	254,772	303,592
Total liabilities and stockholders' equity	$ 205,696	221,773	232,747	244,109	254,772	303,592
As Reported
Current assets:
Cash and cash equivalents		17,077	19,307	12,794	10,262	22,314
Short-term investments		36,461	28,862	24,739	27,491	18,112
Trade accounts receivable, net		8,327	16,709	13,819	15,392	12,693
Financing receivables, net		2,614	1,890	1,678	1,533	2,004
Income tax receivable		473	483	13,290	13,290	17,369
Inventories		88,024	92,103	101,765	104,540	124,800
Prepaid expenses and other current assets		1,854	1,827	1,855	1,826	1,295
Total current assets		154,830	161,181	169,940	174,334	198,587
Rental equipment, net		20,551	24,485	26,821	30,973	46,036
Property, plant and equipment, net		43,432	44,484	43,477	44,732	48,709
Deferred income tax assets, net		267	247	179	216	4,554
Non-current financing receivables, net		588	427	1,385	1,817	1,516
Prepaid income taxes		1,464	1,843	2,227	2,620	4,095
Other assets		641	80	80	80	95
Total assets		221,773	232,747	244,109	254,772	303,592
Total liabilities and stockholders' equity		221,773	232,747	244,109	254,772	303,592
Adjustment
Current assets:
Inventories		(65,642)	(69,448)	(77,089)	(73,696)	(92,378)
Total current assets		(65,642)	(69,448)	(77,089)	(73,696)	(92,378)
Non-current inventories		$ 65,642	$ 69,448	$ 77,089	$ 73,696	$ 92,378