Debt - Additional Information (Detail) - USD ($) | Jun. 26, 2015 | Dec. 31, 2014 | Aug. 31, 2014 | Sep. 30, 2016 | Sep. 30, 2016 | Sep. 30, 2015 | Jul. 29, 2014 | Jul. 31, 2013 |
Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Maturity date of amended and restated credit agreement | | | | Jul. 30, 2017 | | | | |
Credit facility borrowing base | | | | $ 80,000,000 | $ 80,000,000 | | | |
Credit facility, interest rate description | | | | | The Company's borrowing rates in the credit facility provide for base rate loans at the prime rate (3.5% at September 30, 2016) plus applicable margin utilization rates that range from 1.75% to 2.50%, and LIBO rate loans at LIBO published rates plus applicable utilization rates (2.75% to 3.50% at September 30, 2016). At September 30, 2016, the Company had in place one LIBO rate loan with an effective rate of 3.77%. | | | |
Outstanding borrowings under revolving credit facility | | | | $ 65,000,000 | $ 65,000,000 | | | |
Weighted-average interest rate of borrowings | | | | 4.49% | 4.49% | | | |
Credit facility remaining borrowing capacity | | | | $ 15,000,000 | $ 15,000,000 | | | |
Interest swap agreements period | | | | | 2 years | | | |
Settlement of interest rate swaps | | | | | $ 7,000 | $ 217,000 | | |
Additional Equipment Loan [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument, interest rate, effective percentage | | | 3.40% | | | | | |
Credit facility remaining borrowing capacity | | | $ 1,200,000 | | | | | |
Company's bank debt | | | | 2,950,000 | $ 2,950,000 | | | |
Equipment Loan, face amount | | | | | | | $ 6,000,000 | |
Equipment Loan, monthly payment | | | 87,800 | | | | | |
Equipment Loan, maturity date | | | | | Jul. 31, 2019 | | | |
Additional equipment Loan, drawings | | $ 500,000 | $ 4,800,000 | | | | | |
Equipment Loan, interest rate description | | | | | Interim draws on this facility carried a floating interest rate, payable monthly at the LIBO published rate plus 2.50% and on June 26, 2015 converted into a fixed term loan requiring monthly payments | | | |
Revolving Line of Credit and Letter of Credit Facility [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Credit facility borrowing capacity | | | | $ 250,000,000 | $ 250,000,000 | | | |
Fixed Term Loan [Member] | Additional Equipment Loan [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Equipment Loan, monthly payment | $ 8,700 | | | | | | | |
Equipment Loan, maturity date | | | | | Jun. 26, 2020 | | | |
Prime Rate [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument, interest rate, effective percentage | | | | 3.50% | 3.50% | | | |
London Interbank Offered Rate (LIBOR) [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument, interest rate, effective percentage | | | | 3.77% | 3.77% | | | |
London Interbank Offered Rate (LIBOR) [Member] | Additional Equipment Loan [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
LIBOR rate loans | | | | | 2.50% | | | |
Base Rate And Libor [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument basis weighted average interest rate spread on variable rate | | | | 3.82% | 3.82% | 3.39% | | |
Equipment Loan [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument, interest rate, effective percentage | | | | 3.95% | 3.95% | | | |
Company's bank debt | | | | $ 3,380,000 | $ 3,380,000 | | | |
Equipment Loan, face amount | | | | | | | | $ 10,000,000 |
Equipment Loan, monthly payment | | | | | $ 184,000 | | | |
Equipment Loan, maturity date | | | | | Jul. 31, 2018 | | | |
Minimum [Member] | Prime Rate [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
LIBOR rate loans | | | | | 1.75% | | | |
Minimum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
LIBOR rate loans | | | | | 2.75% | | | |
Maximum [Member] | Prime Rate [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
LIBOR rate loans | | | | | 2.50% | | | |
Maximum [Member] | London Interbank Offered Rate (LIBOR) [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
LIBOR rate loans | | | | | 3.50% | | | |
Interest Rate Swap [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Swap agreement date | | | | | 2012-07 | | | |
Commenced date | | | | | 2014-01 | | | |
Termination date | | | | | 2016-01 | | | |
Company's bank debt | | | | $ 75,000,000 | $ 75,000,000 | | | |
Interest Rate Swap [Member] | London Interbank Offered Rate (LIBOR) [Member] | Credit Agreement [Member] | | | | | | | | |
Debt Instrument [Line Items] | | | | | | | | |
Debt instrument, interest rate | | | | 0.563% | 0.563% | | | |