General form of registration statement for all companies including face-amount certificate companies

Equity Method Investments - Additional Information (Detail)

v3.21.2
Equity Method Investments - Additional Information (Detail)
$ in Thousands, shares in Millions
 3 Months Ended 9 Months Ended 12 Months Ended
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Sep. 30, 2021
USD ($)
Sep. 30, 2020
USD ($)
Dec. 31, 2020
USD ($)
shares
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Satellites
Dec. 31, 2017
shares
Schedule of Equity Method Investments [Line Items]                
Long term purchase commitement amount     $ 16,100          
Difference between carrying value of equity method investments and undelying equity in the net assets of the investees         $ 500 $ 0    
Customer advances $ 15,136   15,136   $ 17,096      
LeoStella [Member]                
Schedule of Equity Method Investments [Line Items]                
Payments remitted     $ 15,000 $ 8,200        
Payments to acquire equity method investments             $ 7,000  
LeoStella [Member] | Blacksky Technology [Member]                
Schedule of Equity Method Investments [Line Items]                
Equity method investment ownership percentage         50.00% 50.00% 50.00%  
LeoStella [Member] | Satellite Purchase Contract [Member] | Commitments To Purchase Satellites [Member]                
Schedule of Equity Method Investments [Line Items]                
Long term prchase commitement minimum quantity required | Satellites             20  
Long term purchase commitement amount             $ 79,000  
Purchase commitment amount receivable towards discount             $ 8,800  
Discount received amount         $ 5,100      
Minimum monthly payment agreed         1,000      
Gross payments made towards capital work in progress         8,200 $ 23,300    
LeoStella [Member] | Satellite Purchase Contract [Member] | Commitments To Purchase Satellites [Member] | Intelsat Facility [Member]                
Schedule of Equity Method Investments [Line Items]                
Minimum monthly payment agreed         $ 2,000      
LeoStella [Member] | Thales [Member]                
Schedule of Equity Method Investments [Line Items]                
Equity method investment ownership percentage         50.00% 50.00% 50.00%  
X-Bow [Member]                
Schedule of Equity Method Investments [Line Items]                
Shares purchased during period | shares               13.5
Equity method investment ownership percentage 17.90%   17.90%          
X-Bow [Member] | Stock Subscription And Technology Transfer Agreement [Member]                
Schedule of Equity Method Investments [Line Items]                
Equity method investment ownership percentage         20.60%      
Investment owned number of shares | shares         13.5      
LeoStella And X-Bow [Member]                
Schedule of Equity Method Investments [Line Items]                
Inventory $ 41,100   $ 41,100   $ 47,300 $ 31,900    
Notes payable to related parties         51,400 $ 56,000    
Difference between carrying value of equity method investments and undelying equity in the net assets of the investees 600   600   500      
Customer advances 52,500   52,500   $ 51,400      
Equity Method Investee [Member]                
Schedule of Equity Method Investments [Line Items]                
Revenue from related parties $ 3,500 $ 9,600 $ 20,900 $ 12,900