Basis of presentation (Policies)	9 Months Ended
Sep. 30, 2012
Unaudited condensed consolidated financial statements	*Unaudited condensed consolidated financial statements* The unaudited condensed consolidated financial statements of Power Solutions International, Inc. present information in accordance with generally accepted accounting principles in the U.S. (“GAAP”) and have been prepared pursuant to the rules and regulations of the SEC and in the opinion of management reflect all normal and recurring adjustments necessary to present fairly the interim periods of the unaudited condensed consolidated financial position, results of operations and cash flows of the Company, The W Group and its wholly-owned subsidiaries for the periods presented, including retroactive restatement to reflect the 1-for-32 Reverse Split approved by the stockholders in their vote on the Migratory Merger and Reverse Split, which were effective August 26, 2011 (and described below in Note 4, “Reverse recapitalization of The W Group, private placement, reverse split and migratory merger ” ), as required in accordance with SEC Staff Accounting Bulletin (SAB) Topic 4C Equity Accounts — Change in Capital Structure , and Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 260, Earnings Per Share. Accordingly, the unaudited condensed consolidated balance sheets presented herein reflect a reduction in the aggregate dollar value of common shares issued and outstanding, with a corresponding increase reflected in additional paid-in capital of approximately $0.01 million, as detailed in Note 11, “Stockholders’ equity.” Total authorized shares were unchanged by the Reverse Split. The consummation of the Migratory Merger and Reverse Split, effective on August 26, 2011, also triggered the automatic conversion of the shares of the Company’s preferred stock to Company common stock. In accordance with ASC 260, the conversion of the Company’s preferred stock is presented prospectively from August 26, 2011, resulting in a $9.7 million increase in additional paid in capital and elimination of the Series A Convertible Preferred Stock in the Company’s unaudited condensed consolidated balance sheet as of December 31, 2011, also detailed in Note 11, “Stockholders’ equity.” Earnings per share is calculated based upon the weighted average shares which reflect the conversion of the preferred shares to shares of the Company’s common stock effective August 26, 2011, as restated for the Reverse Split. These unaudited condensed consolidated financial statements should be read in conjunction with, and have been prepared in conformity with the accounting principles reflected in, the consolidated financial statements and related notes included in Power Solutions International Inc’s, Annual Report on Form 10-K for the fiscal year ended December 31, 2011. As these financial statements have been prepared pursuant to the rules and regulations of the SEC, certain information and disclosures normally included in the financial statements and related notes prepared in accordance with GAAP have been condensed or omitted.
Principles of consolidation	*Principles of consolidation* The unaudited condensed consolidated financial statements include the accounts of The W Group, Inc., a wholly-owned subsidiary of Power Solutions International, Inc., and its wholly-owned subsidiaries, Power Production, Inc., Power Great Lakes, Inc., Power Solutions, Inc., Power Global Solutions, Inc., Auto Manufacturing, Inc., Torque Power Source Parts, Inc., XISync, LLC, PSI International, LLC, and Power Properties, L.L.C. Collectively, these entities produce and distribute off-highway industrial engines and provide aftermarket support for the industrial engine market. All significant intercompany balances and transactions have been eliminated in consolidation.
Significant accounting policies	*Significant accounting policies* The Company’s significant accounting policies as of December 31, 2011, are described in the Company’s annual report, dated March 30, 2012, filed on Form 10-K with the Securities and Exchange Commission. There have been no material changes with respect to the Company’s significant accounting policies subsequent to December 31, 2011, with the exception of cash and cash equivalents and equity-based compensation. Prior to its March 20, 2012 amendment, the Company’s loan and security agreement with Harris N.A. (now known as BMO Harris Bank, N.A (“BMO Bank”)) (“Harris Agreement”), required that cash received be applied against the Company’s revolving line of credit. Accordingly, the Company did not maintain cash or cash equivalents on its consolidated balance sheet, but instead funded its operations through borrowings under its revolving line of credit. As further described in Note 9, “Revolving line of credit,” the Harris Agreement was amended effective March 20, 2012, and among other changes, cash balances are no longer automatically swept by BMO Bank and applied against the revolving line of credit. Under ASC 470-10-45, Debt, the elimination of the automatic sweeping of the Company’s cash and applying it against the revolving line of credit results in a change in the presentation of the revolving line of credit from a current liability to a long-term obligation on the Company’s consolidated balance sheet. Accordingly, the Company has presented the revolving line of credit as a long-term obligation on its consolidated balance sheet subsequent to March 20, 2012, the effective date of the Amended Agreement. At September 30, 2012, the Company had a cash balance recorded on its consolidated balance sheet. Management has adopted a significant accounting policy based on this change. Management has also adopted an additional significant accounting policy based on the Compensation Committee of the Board approving the 2012 Incentive Compensation Plan (See Note 12, “2012 Incentive compensation plan”) and granting Stock Appreciation Rights (“SAR”).Both of these policies are presented below.
Cash and cash equivalents	Cash and cash equivalents The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.
Equity-based compensation	Equity-based compensation The Company accounts for equity-based compensation expense for awards granted to employees for service over the service period based on the grant date fair value. Furthermore, the SAR granted is accounted for as equity, in accordance with ASC 718-10-25, Determining Whether to Classify a Financial Instrument as a Liability or As Equity.
Business Combinations	In accordance with ASC 805, Business Combinations, The W Group was considered the accounting acquiror in the reverse acquisition.
Earnings Per Share	The Company computes earnings per share by applying the guidance stated in ASC 260, Earnings per Share, to determine the net income (loss) available per share of its common stock.
Financial Instruments	As of September 30, 2012, the Company’s Private Placement Warrants were measured at fair value under ASC Topic 820, Fair Value Measurements and Disclosures of the Accounting Standards Codification.
Distinguishing Liabilities from Equity	The Company analyzes financial instruments with features of both liabilities and equity under ASC 480, Distinguishing Liabilities from Equity
Derivatives and Hedging	ASC 480, Distinguishing Liabilities from Equity, and ASC 815, Derivatives and Hedging.

Basis of presentation (Policies)

9 Months Ended

Sep. 30, 2012

Unaudited condensed consolidated financial statements

Unaudited condensed consolidated financial statements

The unaudited condensed consolidated financial statements of Power Solutions International, Inc. present information in accordance with generally accepted accounting principles in the U.S. (“GAAP”) and have been prepared pursuant to the rules and regulations of the SEC and in the opinion of management reflect all normal and recurring adjustments necessary to present fairly the interim periods of the unaudited condensed consolidated financial position, results of operations and cash flows of the Company, The W Group and its wholly-owned subsidiaries for the periods presented, including retroactive restatement to reflect the 1-for-32 Reverse Split approved by the stockholders in their vote on the Migratory Merger and Reverse Split, which were effective August 26, 2011 (and described below in Note 4, “Reverse recapitalization of The W Group, private placement, reverse split and migratory merger ” ), as required in accordance with SEC Staff Accounting Bulletin (SAB) Topic 4C Equity Accounts — Change in Capital Structure , and Financial Accounting Standards Board (“FASB”) Accounting Standards Codification (“ASC”) 260, Earnings Per Share. Accordingly, the unaudited condensed consolidated balance sheets presented herein reflect a reduction in the aggregate dollar value of common shares issued and outstanding, with a corresponding increase reflected in additional paid-in capital of approximately $0.01 million, as detailed in Note 11, “Stockholders’ equity.” Total authorized shares were unchanged by the Reverse Split. The consummation of the Migratory Merger and Reverse Split, effective on August 26, 2011, also triggered the automatic conversion of the shares of the Company’s preferred stock to Company common stock. In accordance with ASC 260, the conversion of the Company’s preferred stock is presented prospectively from August 26, 2011, resulting in a $9.7 million increase in additional paid in capital and elimination of the Series A Convertible Preferred Stock in the Company’s unaudited condensed consolidated balance sheet as of December 31, 2011, also detailed in Note 11, “Stockholders’ equity.” Earnings per share is calculated based upon the weighted average shares which reflect the conversion of the preferred shares to shares of the Company’s common stock effective August 26, 2011, as restated for the Reverse Split.

These unaudited condensed consolidated financial statements should be read in conjunction with, and have been prepared in conformity with the accounting principles reflected in, the consolidated financial statements and related notes included in Power Solutions International Inc’s, Annual Report on Form 10-K for the fiscal year ended December 31, 2011. As these financial statements have been prepared pursuant to the rules and regulations of the SEC, certain information and disclosures normally included in the financial statements and related notes prepared in accordance with GAAP have been condensed or omitted.

Principles of consolidation

Principles of consolidation

The unaudited condensed consolidated financial statements include the accounts of The W Group, Inc., a wholly-owned subsidiary of Power Solutions International, Inc., and its wholly-owned subsidiaries, Power Production, Inc., Power Great Lakes, Inc., Power Solutions, Inc., Power Global Solutions, Inc., Auto Manufacturing, Inc., Torque Power Source Parts, Inc., XISync, LLC, PSI International, LLC, and Power Properties, L.L.C. Collectively, these entities produce and distribute off-highway industrial engines and provide aftermarket support for the industrial engine market. All significant intercompany balances and transactions have been eliminated in consolidation.

Significant accounting policies

Significant accounting policies

The Company’s significant accounting policies as of December 31, 2011, are described in the Company’s annual report, dated March 30, 2012, filed on Form 10-K with the Securities and Exchange Commission. There have been no material changes with respect to the Company’s significant accounting policies subsequent to December 31, 2011, with the exception of cash and cash equivalents and equity-based compensation. Prior to its March 20, 2012 amendment, the Company’s loan and security agreement with Harris N.A. (now known as BMO Harris Bank, N.A (“BMO Bank”)) (“Harris Agreement”), required that cash received be applied against the Company’s revolving line of credit. Accordingly, the Company did not maintain cash or cash equivalents on its consolidated balance sheet, but instead funded its operations through borrowings under its revolving line of credit. As further described in Note 9, “Revolving line of credit,” the Harris Agreement was amended effective March 20, 2012, and among other changes, cash balances are no longer automatically swept by BMO Bank and applied against the revolving line of credit. Under ASC 470-10-45, Debt, the elimination of the automatic sweeping of the Company’s cash and applying it against the revolving line of credit results in a change in the presentation of the revolving line of credit from a current liability to a long-term obligation on the Company’s consolidated balance sheet. Accordingly, the Company has presented the revolving line of credit as a long-term obligation on its consolidated balance sheet subsequent to March 20, 2012, the effective date of the Amended Agreement. At September 30, 2012, the Company had a cash balance recorded on its consolidated balance sheet. Management has adopted a significant accounting policy based on this change. Management has also adopted an additional significant accounting policy based on the Compensation Committee of the Board approving the 2012 Incentive Compensation Plan (See Note 12, “2012 Incentive compensation plan”) and granting Stock Appreciation Rights (“SAR”).Both of these policies are presented below.

Cash and cash equivalents

Cash and cash equivalents

The Company considers all highly liquid investments with an original maturity of three months or less when purchased to be cash equivalents.

Equity-based compensation

Equity-based compensation

The Company accounts for equity-based compensation expense for awards granted to employees for service over the service period based on the grant date fair value. Furthermore, the SAR granted is accounted for as equity, in accordance with ASC 718-10-25, Determining Whether to Classify a Financial Instrument as a Liability or As Equity.

Business Combinations

In accordance with ASC 805, Business Combinations, The W Group was considered the accounting acquiror in the reverse acquisition.

Earnings Per Share

The Company computes earnings per share by applying the guidance stated in ASC 260, Earnings per Share, to determine the net income (loss) available per share of its common stock.

Financial Instruments

As of September 30, 2012, the Company’s Private Placement Warrants were measured at fair value under ASC Topic 820, Fair Value Measurements and Disclosures of the Accounting Standards Codification.

Distinguishing Liabilities from Equity

The Company analyzes financial instruments with features of both liabilities and equity under ASC 480, Distinguishing Liabilities from Equity

Derivatives and Hedging

ASC 480, Distinguishing Liabilities from Equity, and ASC 815, Derivatives and Hedging.