Detail of Selected Balance Sheet Accounts (Cost and Estimated Earnings on Uncompleted Contracts) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Sep. 30, 2014
Balance Sheet Related Disclosures [Abstract]
Costs incurred on uncompleted contracts	$ 618,778	$ 604,939
Estimated earnings	161,724powl_EstimatedEarnings	157,562powl_EstimatedEarnings
Total	780,502	762,501
Less: Billings to date	(747,964)us-gaap_BilledContractReceivables	(715,233)us-gaap_BilledContractReceivables
Net underbilled position	32,538us-gaap_UnbilledContractsReceivable	47,268us-gaap_UnbilledContractsReceivable
Included in the accompanying balance sheets under the following captions:
Costs and estimated earnings in excess of billings on uncompleted contracts - underbilled	96,709	95,970
Billings in excess of costs and estimated earnings on uncompleted contracts - overbilled	(64,171)us-gaap_BillingsInExcessOfCostCurrent	(48,702)us-gaap_BillingsInExcessOfCostCurrent
Net underbilled position	$ 32,538us-gaap_UnbilledContractsReceivable	$ 47,268us-gaap_UnbilledContractsReceivable

Costs incurred on uncompleted contracts.

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Estimated earnings.

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Amounts due for billed services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the Company and, at a minimum, one other party. An example would be amounts billed to customers under contracts or programs but not paid as of the balance sheet date.

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-Publisher SEC

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-Number 210

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Liability attributable to (i) billings in excess of costs under the percentage of completion contract accounting method representing the difference between contractually invoiced amounts (billings) and revenue recognized based, for example, on costs incurred to estimated total costs at period end or (ii) contractually invoiced amounts (billings) in excess of costs incurred and accumulated under the completed contract accounting method that are expected to be realized within one year or one operating cycle, whichever is longer, from the reporting date.

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Amount of receivable reflecting the cost incurred on uncompleted contracts in excess of related billings which is expected to be collected within one year or the normal operating cycle, if longer.

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Amount to be collected within one year of the balance sheet date (or one operating cycle, if longer) from customers in accordance with the contractual provisions of long-term contracts or programs including amounts billed and unbilled as of the balance sheet date.

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Unbilled amounts due for services rendered or to be rendered, actions taken or to be taken, or a promise to refrain from taking certain actions in accordance with the terms of a legally binding agreement between the entity and, at a minimum, one other party. An example would be amounts associated with contracts or programs where the recognized revenue for performance thereunder exceeds the amounts billed under the terms thereof as of the date of the balance sheet.

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