Commitments, Guarantees and Other Contingencies - Additional Information (Detail) (USD $)	Mar. 31, 2013	Dec. 31, 2012
Recorded Unconditional Purchase Obligation [Line Items]
Maximum potential commitment under letters of credit	$ 3,100,000	$ 3,600,000
Reserve for unfunded lending commitments	$ 609,000	$ 367,000

Maximum potential commitment under letters of credit.

No definition available.

Name:	plmt_MaximumPotentialCommitmentUnderLettersOfCredit
Namespace Prefix:	plmt_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant