COMMITMENTS AND CONTINGENCIES (Details) (Indemnification Agreement, USD $) In Millions, unless otherwise specified	Dec. 31, 2011
Indemnification Agreement
Commitments and contingencies
Indemnification agreement with certain officers, maximum	$ 10

Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under each individual guarantee agreement.

No definition available.

Name:	pl_GuarantorObligationsMaximumExposurePerAgreement
Namespace Prefix:	pl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant