Government Contracts - Additional Information (Detail) $ in Thousands		1 Months Ended			3 Months Ended		6 Months Ended		12 Months Ended
	Jul. 01, 2019 USD ($)	May 31, 2021 USD ($) Option	Jul. 31, 2018 USD ($)	Jun. 30, 2016 USD ($) Option	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Jun. 30, 2022 USD ($)	Jun. 30, 2021 USD ($)	Dec. 31, 2021 USD ($) Option	Jan. 19, 2022 USD ($)	Jan. 31, 2020 USD ($)	May 31, 2019 USD ($)
Government Contracts [Line Items]
Grant revenue					$ 1,993	$ 5,148	$ 4,062	$ 12,448
BARDA and DTRA [Member]
Government Contracts [Line Items]
Maximum potential funding from government contract					69,700		69,700
Potential grant amount exercised					12,700		12,700
Grant [Member] | DoD, CDMRP and JWMRP [Member] | Maximum [Member]
Government Contracts [Line Items]
Grant revenue					100		1,000
Grant [Member] | DoD, CDMRP and JWMRP [Member] | Minimum [Member]
Government Contracts [Line Items]
Grant revenue						1,100		1,800
SPR206 [Member] | DoD, CDMRP and JWMRP [Member]
Government Contracts [Line Items]
Award received for clinical development	$ 5,900
Non-dilutive funding period	4 years
BARDA [Member]
Government Contracts [Line Items]
Potential contract amount awarded			$ 44,200							$ 59,700
Potential amount additional funding awarded										12,900
Overall potential award increased										$ 46,900
BARDA [Member] | Base Period Contracts [Member]
Government Contracts [Line Items]
Potential amount initial funding awarded			$ 15,700									$ 18,200
Potential amount additional funding awarded												2,500
Overall potential award increased												$ 46,800
Contract term			3 years
BARDA [Member] | Grant [Member]
Government Contracts [Line Items]
Grant revenue					700	1,900	1,300	8,200
BARDA [Member] | First Option [Member]
Government Contracts [Line Items]
Potential amount additional funding awarded											$ 15,900
Potential amount increase in committed funding											34,000
BARDA [Member] | Second Option [member]
Government Contracts [Line Items]
Potential grant amount awarded											$ 12,700
DTRA [Member] | Maximum [Member]
Government Contracts [Line Items]
Potential amount additional funding awarded					10,000		10,000
Niaid [Member] | Spero Cantab [Member] | Cantab Anti Infectives Ltd. [Member] | Cantab Agreements [Member]
Government Contracts [Line Items]
Maximum potential funding from government contract				$ 6,500
Number of option period for funding from government contract | Option				3
Niaid [Member] | Grant [Member] | Spero Cantab [Member] | Cantab Anti Infectives Ltd. [Member] | Cantab Agreements [Member]
Government Contracts [Line Items]
Grant revenue					0	$ 100	0	$ 400
Niaid [Member] | SPR206 [Member]
Government Contracts [Line Items]
Contract term		5 years
Grant revenue					$ 400		600
Award received for clinical development		$ 23,400
Number of option period for funding from government contract | Option		5
Committed amount from government contract							$ 2,100
Niaid [Member] | First Option [Member] | Spero Cantab [Member] | Cantab Anti Infectives Ltd. [Member] | Cantab Agreements [Member]
Government Contracts [Line Items]
Number of option period for funding from government contract | Option									2
Committed amount from government contract									$ 5,900