LEASE LINE TO THIRD PARTY (Details) (USD $) In Millions	9 Months Ended
Sep. 30, 2011	Mar. 31, 2011
Capital Leases, Future Minimum Payments Receivable [Abstract]
2011 (remaining 3 months)	$ 0.1
2012	0.6
2013	0.6
2014	0.6
2015	0.6
Thereafter	1.7
Total	4.2
Capital Leases of Lessor [Abstract]
Lease line maximum borrowing capacity		15.5
Future lease payments period	four to eight year
Noncontrolling Interest [Member] \| Semi South [Member]
Capital Leases of Lessor [Abstract]
Lease line maximum borrowing capacity	8.6
Lease line funded amount	8.0
Lease line funded amount, less payments withheld under arrangement to finance capital equipment	3.9
Lease line funded as deposits on equipment	$ 4.1

Capital Leases, Direct Financing Leases, Amount Funded As Deposits On Equipment

Name:	powi_CapitalLeasesDirectFinancingLeasesAmountFundedAsDepositsOnEquipment
Namespace Prefix:	powi
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Direct Financing Leases, Amount Funded To Finance Capital Equipment

+ Details

Name:	powi_CapitalLeasesDirectFinancingLeasesAmountFundedToFinanceCapitalEquipment
Namespace Prefix:	powi
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Direct Financing Leases, Future Payments Period

+ Details

Name:	powi_CapitalLeasesDirectFinancingLeasesFuturePaymentsPeriod
Namespace Prefix:	powi
Data Type:	us-types:durationStringItemType
Balance Type:	na
Period Type:	duration

- Definition

Capital Leases, Direct Financing Leases, Maximum Borrowing Capacity

+ Details

Name:	powi_CapitalLeasesDirectFinancingLeasesMaximumBorrowingCapacity
Namespace Prefix:	powi
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Capital Leases, Direct Financing Leases, Outstanding Amount

+ Details

Name:	powi_CapitalLeasesDirectFinancingLeasesOutstandingAmount
Namespace Prefix:	powi
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future minimum lease rental payments receivable for the five years following the balance sheet date and the future minimum payment amount in total on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(i)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivable
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Future rental payments receivable within one year of the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableCurrent
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future lease rental payments receivable after the fifth year from the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableDueThereafter
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future lease rental payments receivable within the fifth year from the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableInFiveYears
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future lease rental payments receivable within the fourth year from the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableInFourYears
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future lease rental payments receivable within the third year from the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableInThreeYears
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Future rental payments receivable within the second year from the balance sheet date on nonoperating leases (direct financing, sales-type and leveraged leases).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 13

-Paragraph 23

-Subparagraph a(ii)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 840

-SubTopic 30

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6952072&loc=d3e45377-112738

+ Details

Name:	us-gaap_CapitalLeasesFutureMinimumPaymentsReceivableInTwoYears
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CapitalLeasesOfLessorAbstract
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration