Leases - Maturities of Operating and Finance Lease Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Operating Lease Liabilities, Payments Due [Abstract]
Operating leases, 2022	$ 2,184
Operating leases, 2023	2,269
Operating leases, 2024	1,818
Operating leases, 2025	898
Operating leases, 2026	852
Operating leases, 2027	586
Total operating lease payments	8,607
Less imputed interest, Operating leases	1,436
Total operating lease liabilities	7,171
Finance Lease Liabilities, Payments, Due [Abstract]
Finance leases, 2022	63
Finance leases, 2023	38
Finance leases, 2024	3
Total finance lease payments	104
Less imputed interest, Finance leases	5
Total finance lease liabilities	99
Lessee Lease Liability Payments Due [Abstract]
2022	2,247
2023	2,307
2024	1,821
2025	898
2026	852
2027	586
Total lease payments	8,711
Less imputed interest	1,441
Total lease liabilities	$ 7,270	$ 7,611

Lessee lease liability.

No definition available.

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Balance Type:	credit
Period Type:	instant

- Definition

Lessee lease liability payments due.

+ References

No definition available.

+ Details

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- Definition

Lessee lease liability payments due.

+ References

No definition available.

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- Definition

Lessee lease liability payments due next twelve months.

+ References

No definition available.

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- Definition

Lessee lease liability payments due year five.

+ References

No definition available.

+ Details

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- Definition

Lessee lease liability payments due year four.

+ References

No definition available.

+ Details

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- Definition

Lessee lease liability payments due year six.

+ References

No definition available.

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- Definition

Lessee lease liability payments due year three.

+ References

No definition available.

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- Definition

Lessee lease liability payments due year two.

+ References

No definition available.

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Data Type:	xbrli:monetaryItemType
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- Definition

Lessee leases liability undiscounted excess amount.

+ References

No definition available.

+ Details

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- Definition

Lessee operating lease liability payments due year six.

+ References

No definition available.

+ Details

Name:	sien_LesseeOperatingLeaseLiabilityPaymentsDueYearSix
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Data Type:	xbrli:monetaryItemType
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- References

No definition available.

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Namespace Prefix:	us-gaap_
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Balance Type:	na
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- Definition

Present value of lessee's discounted obligation for lease payments from finance 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=123408670&loc=SL77918701-209980

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

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- Definition

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

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for finance lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ 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 finance lease.

+ References

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- Definition

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

+ References

+ Details

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

- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in next fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fifth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in fourth fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in third fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ References

+ Details

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- Definition

Amount of lessee's undiscounted obligation for lease payment for operating lease to be paid in second fiscal year following current fiscal year. Excludes interim and annual periods when interim periods are reported from current statement of financial position date (rolling approach).

+ 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.

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- References

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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.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=123391704&loc=SL77918627-209977

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