Cash Equivalents and Investments in Marketable Securities - Summary of Cash Equivalents and Investments in Marketable Securities (Details) $ in Thousands	Dec. 31, 2018 USD ($)
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 21,691
Money market funds
Debt Securities, Available-for-sale [Line Items]
Fair Value	4,830
Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value	1,497
Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	6,989
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value	8,375
Fair Value, Measurements, Recurring
Debt Securities, Available-for-sale [Line Items]
Fair Value	21,691
Cash equivalents	7,829
Marketable securities at fair value	13,862
Total	21,691
Fair Value, Measurements, Recurring \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Fair Value	4,830
Fair Value, Measurements, Recurring \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value	1,497
Fair Value, Measurements, Recurring \| Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	6,989
Fair Value, Measurements, Recurring \| U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value	8,375
Fair Value, Measurements, Recurring \| Quoted prices in active market Level 1
Debt Securities, Available-for-sale [Line Items]
Fair Value	13,205
Fair Value, Measurements, Recurring \| Quoted prices in active market Level 1 \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Fair Value	4,830
Fair Value, Measurements, Recurring \| Quoted prices in active market Level 1 \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Quoted prices in active market Level 1 \| Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Quoted prices in active market Level 1 \| U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value	8,375
Fair Value, Measurements, Recurring \| Significant other observable inputs Level 2
Debt Securities, Available-for-sale [Line Items]
Fair Value	8,486
Fair Value, Measurements, Recurring \| Significant other observable inputs Level 2 \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant other observable inputs Level 2 \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value	1,497
Fair Value, Measurements, Recurring \| Significant other observable inputs Level 2 \| Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	6,989
Fair Value, Measurements, Recurring \| Significant other observable inputs Level 2 \| U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs Level 3
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs Level 3 \| Money market funds
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs Level 3 \| Commercial paper
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs Level 3 \| Corporate notes and bonds
Debt Securities, Available-for-sale [Line Items]
Fair Value	0
Fair Value, Measurements, Recurring \| Significant unobservable inputs Level 3 \| U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Fair Value	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 326
-SubTopic 30
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=118942338&loc=SL82898722-210454

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118954083&loc=d3e26610-111562

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (aa)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=d3e27161-111563

+ Details

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

- Definition

Cash includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the customer may deposit additional funds at any time and effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid Investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months. Short-term investments, exclusive of cash equivalents, generally consist of marketable securities intended to be sold within one year (or the normal operating cycle if longer) and may include trading securities, available-for-sale securities, or held-to-maturity securities (if maturing within one year), as applicable.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.1)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Amount of short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation.

+ References

+ Details

Name:	us-gaap_CashEquivalentsAtCarryingValue
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

- Definition

Amount of investments including trading securities, available-for-sale securities, held-to-maturity securities, and short-term investments classified as other and current.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(4))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(6))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(5))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(1)(g))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

Reference 5: http://fasb.org/us-gaap/role/ref/legacyRef
-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_ShortTermInvestments
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

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

- Details

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

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=zsan_U.S.TreasuriesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByMeasurementFrequencyAxis=us-gaap_FairValueMeasurementsRecurringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: