Fair Value Measurements - Financial Instruments Measured at Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Corporate bonds
Assets
Debt securities	$ 82,086	$ 100,258
Preferred stock
Assets
Preferred stock	21,603	0
Recurring
Assets
Debt securities		100,334
Marketable securities	103,689
Liabilities
Total liabilities	54,834
Recurring \| U.S. treasury securities
Assets
Debt securities	0	76
Recurring \| Corporate bonds
Assets
Debt securities	82,086	100,258
Preferred stock		0
Recurring \| Preferred stock
Assets
Preferred stock	21,603
Recurring \| Warrant liabilities
Liabilities
Warrant liabilities	46,051	5,241
Recurring \| Conversion option liability
Liabilities
Conversion option liability	8,783
Recurring \| Level 1
Assets
Debt securities		76
Marketable securities	0
Liabilities
Total liabilities	12,377
Recurring \| Level 1 \| U.S. treasury securities
Assets
Debt securities	0	76
Recurring \| Level 1 \| Corporate bonds
Assets
Debt securities	0	0
Preferred stock		0
Recurring \| Level 1 \| Preferred stock
Assets
Preferred stock	0
Recurring \| Level 1 \| Warrant liabilities
Liabilities
Warrant liabilities	12,377	0
Recurring \| Level 1 \| Conversion option liability
Liabilities
Conversion option liability	0
Recurring \| Level 2
Assets
Debt securities		100,258
Marketable securities	103,689
Liabilities
Total liabilities	0
Recurring \| Level 2 \| U.S. treasury securities
Assets
Debt securities	0	0
Recurring \| Level 2 \| Corporate bonds
Assets
Debt securities	82,086	100,258
Preferred stock		0
Recurring \| Level 2 \| Preferred stock
Assets
Preferred stock	21,603
Recurring \| Level 2 \| Warrant liabilities
Liabilities
Warrant liabilities	0	0
Recurring \| Level 2 \| Conversion option liability
Liabilities
Conversion option liability	0
Recurring \| Level 3
Assets
Debt securities		0
Marketable securities	0
Liabilities
Total liabilities	42,457
Recurring \| Level 3 \| U.S. treasury securities
Assets
Debt securities	0	0
Recurring \| Level 3 \| Corporate bonds
Assets
Debt securities	0	0
Preferred stock		0
Recurring \| Level 3 \| Preferred stock
Assets
Preferred stock	0
Recurring \| Level 3 \| Warrant liabilities
Liabilities
Warrant liabilities	33,674	$ 5,241
Recurring \| Level 3 \| Conversion option liability
Liabilities
Conversion option liability	$ 8,783

Warrant, Conversion Option Liability

No definition available.

Name:	bhil_WarrantConversionOptionLiability
Namespace Prefix:	bhil_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Warrant Liability, Fair Value Disclosure

+ References

No definition available.

+ Details

Name:	bhil_WarrantLiabilityFairValueDisclosure
Namespace Prefix:	bhil_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- References

No definition available.

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-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=120398452&loc=d3e534808-122878

Reference 2: 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=124258926&loc=SL82898722-210454

Reference 3: 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=124260329&loc=d3e26610-111562

Reference 4: 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=123581744&loc=d3e27161-111563

+ Details

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

- Definition

Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=123594786&loc=SL75136599-209740

+ Details

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

- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

+ References

No definition available.

+ Details

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

- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

+ Details

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

- References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=us-gaap_EquitySecuritiesMember
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_FinancialInstrumentAxis=us-gaap_USTreasurySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_FinancialInstrumentAxis=bhil_ConversionOptionLiabilityMember
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: