Quarterly report pursuant to Section 13 or 15(d)

Stock Based Compensation - Additional Information (Detail)

v3.22.1
Stock Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended
Mar. 31, 2022
Mar. 31, 2021
Defined Benefit Plan Disclosure [Line Items]    
Proceeds from exercise of stock options $ 638 $ 295
Weighted average grant-date fair value   $ 3.46
Employee Stock Option [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Purchase Price of Common Stock, Percent 85.00%  
Restricted Stock Units (RSUs)    
Defined Benefit Plan Disclosure [Line Items]    
Weighted average grant-date fair value $ 2.89  
Unrecognized stock-based compensation expense $ 35,931  
Unrecognized stock-based compensation expense, weighted-average recognition period 2 years 8 months 4 days  
Old Spire Options [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Stockholders Equity Note Stock Split Exchange Ratio 1.8282  
2021 Equity Incentive Plan [Member] | Employee Stock Option [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Share based compensation arrangement,Number of shares available for grant under the plan 3,194,000  
2021 Equity Incentive Plan [Member] | Restricted Stock Units (RSUs)    
Defined Benefit Plan Disclosure [Line Items]    
Share based compensation arrangement,Number of shares available for grant under the plan 8,863,749  
2021 Equity Incentive Plan [Member] | Common Class A [Member]    
Defined Benefit Plan Disclosure [Line Items]    
Number of shares issued under share-based payment arrangement 23,951,000  
Percentage of Outstanding Stock Maximum 5.00%