The number of options to extend the lease under the lessee's operating leasing arrangement.

No definition available.

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- Definition

Allowance for tenant improvements to the office space included in the lessee's operating lease.

+ References

No definition available.

+ Details

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- Definition

Initial letter of credit provided to lessor to secure lease obligation under lessee's operating lease.

+ References

No definition available.

+ Details

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- Definition

Letter of credit provided to lessor to secure lease obligation under lessee's operating lease on the fifth anniversary of the rent commencement date.

+ References

No definition available.

+ Details

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- Definition

Letter of credit provided to lessor to secure lease obligation under lessee's operating lease on the third anniversary of the rent commencement date.

+ References

No definition available.

+ Details

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- Definition

Period of time in which the rent is free under operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- References

No definition available.

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918701-209980

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due after fifth fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in next fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fifth fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in fourth fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in third fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments for operating lease, due in second fiscal year following latest fiscal year.

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payments in excess of discounted obligation for lease payments for operating lease.

+ References

+ Details

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- Definition

Term of lessee's operating lease renewal, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
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- Definition

Term of lessee's operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

+ References

+ Details

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- Definition

Amount of operating lease expense. Excludes sublease income.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77888419&loc=SL77918638-209977

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- References

No definition available.

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Balance Type:	na
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- Definition

Present value of lessee's discounted obligation for lease payments from operating lease.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Present value of lessee's discounted obligation for lease payments from operating lease, classified as current.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes current operating lease liability.

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Data Type:	srt-types:extensibleListItemType
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Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes noncurrent operating lease liability.

+ References

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Data Type:	srt-types:extensibleListItemType
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Period Type:	instant

- Definition

Amount of cash outflow from operating lease, excluding payments to bring another asset to condition and location necessary for its intended use.

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-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (g)(1)
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+ Details

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

- Definition

Amount of lessee's right to use underlying asset under operating lease.

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Indicates line item in statement of financial position that includes operating lease right-of-use asset.

+ References

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Namespace Prefix:	us-gaap_
Data Type:	srt-types:extensibleListItemType
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- Definition

Weighted average discount rate for operating lease calculated at point in time.

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-Publisher FASB
-Name Accounting Standards Codification
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Weighted average remaining lease term for operating lease, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Data Type:	xbrli:durationItemType
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- Details

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Period Type:

- Details

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Long-Term Obligations and Commitments, Operating Leases (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($) Option	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Operating Leases [Abstract]
Right-of-use operating lease assets	$ 12,600
Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List]	us-gaap:OtherAssetsNoncurrent
Operating lease liabilities	$ 17,235
Weighted average remaining lease term	8 years 1 month 6 days
Weighted average discount rate	7.60%
Current portion of operating lease liabilities	$ 2,000
Operating Lease, Liability, Current, Statement of Financial Position [Extensible List]	us-gaap:LongTermDebtAndCapitalLeaseObligationsCurrent
Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List]	ions:LongTermObligationsNoncurrent
Operating lease cash payments	$ 3,900
Annual Future Payments for Operating Lease Liabilities [Abstract]
2020	3,285
2021	3,022
2022	2,781
2023	2,520
2024	2,396
Thereafter	9,465
Total minimum lease payments	23,469
Imputed interest	(6,234)
Total operating lease liabilities	17,235
Rent expense	$ 3,600	$ 2,600	$ 1,700
Office and Laboratory Space Adjacent to Manufacturing Facility [Member]
Operating Leases [Abstract]
Number of options to extend lease \| Option	2
Term of lease extension	5 years
Office Space Subleased to Akcea [Member]
Operating Leases [Abstract]
Number of options to extend lease \| Option	1
Term of lease extension	5 years
Akcea [Member] \| Office Space for Corporate Headquarters [Member]
Operating Leases [Abstract]
Term of lease extension	5 years
Term of lease	123 months
Period of free rent under lease	3 months
Tenant improvement allowance	$ 3,800
Initial amount of letter of credit	2,400
Letter of credit on third anniversary of rent commencement date	1,800
Letter of credit on fifth anniversary of rent commencement date	$ 1,200