Reservation payment that will be credited against future purchases of batches under the agreement.

No definition available.

Name:	ptla_CommercialSupplyAgreementReservationPayment
Namespace Prefix:	ptla_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Upfront payment that will be credited against future purchases of batches under the agreement.

+ References

No definition available.

+ Details

Name:	ptla_CommercialSupplyAgreementUpfrontPayment
Namespace Prefix:	ptla_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Payments related to commercial supply agreement.

+ References

No definition available.

+ Details

Name:	ptla_PaymentsRelatedToCommercialSupplyAgreement
Namespace Prefix:	ptla_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The minimum amount the entity agreed to spend under the long-term purchase commitment.

+ References

No definition available.

+ Details

Name:	us-gaap_LongTermPurchaseCommitmentAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

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

- Definition

Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_LongtermPurchaseCommitmentPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of the loss on termination of a contract for default.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 912

-SubTopic 20

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6539154&loc=d3e52595-109384

+ Details

Name:	us-gaap_LossOnContractTerminationForDefault
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of asset related to consideration paid in advance for costs that provide economic benefits in future periods, and amount of other assets that are expected to be realized or consumed after one year or the normal operating cycle, if longer.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

+ Details

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

- Details

Name:	us-gaap_LongTermPurchaseCommitmentByCategoryOfItemPurchasedAxis=ptla_CMCICOSBiologicsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Commercial Supply Agreement - Additional Information (Detail) (USD $)	1 Months Ended	3 Months Ended
	Jul. 31, 2014	Mar. 31, 2015	Dec. 31, 2014	Nov. 01, 2014
Long Term Purchase Commitment [Line Items]
Prepaid and other long-term assets		$ 14,678,000	$ 15,612,000
CMC ICOS Biologics Inc
Long Term Purchase Commitment [Line Items]
Commercial supply agreement upfront payment	10,000,000
Commercial supply (manufacturing services) agreement reservation payment				4,600,000
Commercial agreement fixed commitment amount	293,900,000
Payments related to commercial supply agreement		6,400,000
Term of commercial supply agreement		7 years
CMC ICOS Biologics Inc \| Upfront Fee
Long Term Purchase Commitment [Line Items]
Prepaid and other long-term assets		14,600,000
CMC ICOS Biologics Inc \| Minimum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	5,000,000
CMC ICOS Biologics Inc \| Maximum
Long Term Purchase Commitment [Line Items]
Termination fees payment under obligation	$ 30,000,000