SCHEDULE II - Valuation and Qualifying Accounts (Detail) - Allowance for Distribution Fees, Discounts and Chargebacks - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Valuation And Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 246	$ 201
Additions, Provision Related to Current Period Sales	24,613	12,837	$ 2,163
Deductions, Actual Distribution Fees, Discounts and Chargebacks Related to Current Period Sales	(22,773)	(12,591)	(1,962)
Deductions, Actual Distribution Fees, Discounts and Chargebacks Related to Prior Period Sales	(246)	(201)
Balance at End of Period	$ 1,840	$ 246	$ 201

Valuation allowances and reserves deductions related prior period.

No definition available.

Name:	acad_ValuationAllowancesAndReservesDeductionsRelatedPriorPeriod
Namespace Prefix:	acad_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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:	srt_ValuationAndQualifyingAccountsDisclosureLineItems
Namespace Prefix:	srt_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of valuation and qualifying accounts and reserves.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 235
-SubTopic 10
-Section S99
-Paragraph 4
-Subparagraph (SX 210.12-09)
-URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e24092-122690

+ Details

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

- Definition

Amount of increase in valuation and qualifying accounts and reserves from charge to cost and expense.

+ References

+ Details

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

- Definition

Amount of decrease in valuation and qualifying accounts and reserves.

+ References

+ Details

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

- Details

Name:	us-gaap_ValuationAllowancesAndReservesTypeAxis=acad_AllowanceForDistributionFeesDiscountsAndChargebacksMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: