FINANCIAL INSTRUMENTS (Details 2) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Measurements
Cost	$ 317,722	$ 136,683
Gross Unrealized Gains	0	19
Gross Unrealized Losses	(454)	(49)
Level 2
Fair Value Measurements
Fair Value	317,268	136,653
Short-term:
Fair Value Measurements
Cost	257,456
Gross Unrealized Gains	0
Gross Unrealized Losses	(235)
Short-term: \| Level 2
Fair Value Measurements
Fair Value	257,221
Short-term: \| Asset-backed Securities
Fair Value Measurements
Cost	28,338	9,012
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(37)	(2)
Short-term: \| Asset-backed Securities \| Level 2
Fair Value Measurements
Fair Value	28,301	9,010
Short-term: \| Commercial Paper
Fair Value Measurements
Cost	48,999	39,530
Gross Unrealized Gains	0	8
Gross Unrealized Losses	(23)	(15)
Short-term: \| Commercial Paper \| Level 2
Fair Value Measurements
Fair Value	48,976	39,523
Short-term: \| Corporate bonds
Fair Value Measurements
Cost	180,119	88,141
Gross Unrealized Gains	0	11
Gross Unrealized Losses	(175)	(32)
Short-term: \| Corporate bonds \| Level 2
Fair Value Measurements
Fair Value	179,944	$ 88,120
Long-term:
Fair Value Measurements
Cost	60,266
Gross Unrealized Gains	0
Gross Unrealized Losses	(219)
Long-term: \| Level 2
Fair Value Measurements
Fair Value	60,047
Long-term: \| Asset-backed Securities
Fair Value Measurements
Cost	23,836
Gross Unrealized Gains	0
Gross Unrealized Losses	(79)
Long-term: \| Asset-backed Securities \| Level 2
Fair Value Measurements
Fair Value	23,757
Long-term: \| Corporate bonds
Fair Value Measurements
Cost	36,430
Gross Unrealized Gains	0
Gross Unrealized Losses	(140)
Long-term: \| Corporate bonds \| Level 2
Fair Value Measurements
Fair Value	$ 36,290

This item represents the cost of debt securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27161-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.2)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_AvailableForSaleDebtSecuritiesAmortizedCostBasis
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

+ Details

Name:	us-gaap_AvailableForSaleSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

+ Details

Name:	us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_ShortTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_AssetBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CommercialPaperMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_CorporateBondSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancialInstrumentAxis=pcrx_LongTermInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: