Cash, Cash Equivalents and Investments - Additional Information (Details)	12 Months Ended
Dec. 31, 2017
Cash And Cash Equivalents [Abstract]
Maximum contractual maturities due for available-for-sale investments	1 year

Available for sale investments maximum contractual maturities period.

No definition available.

Name:	pi_AvailableForSaleInvestmentsMaximumContractualMaturitiesPeriod
Namespace Prefix:	pi_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration