Annual report pursuant to Section 13 and 15(d)

Business combinations and disposals - Schedule of Goodwill (Details)

v3.20.2
Business combinations and disposals - Schedule of Goodwill (Details) - USD ($)
 12 Months Ended
Sep. 30, 2020
Sep. 30, 2019
Changes in goodwill    
Balance at the beginning of the period $ 584,469,000 $ 399,882,000
Goodwill acquired through acquisition 7,652,000  
Other   372,000
Disposal of Q2 Administrators, LLC (899,000)  
Foreign currency translation 1,907,000 (1,772,000)
Balance at the end of the period 593,129,000 584,469,000
Goodwill impairment loss 0  
General Dynamics Information Technology's Citizen Engagement Centers    
Changes in goodwill    
Goodwill acquired through acquisition   184,640,000
Balance at the end of the period 184,640,000  
GT Hiring Solutions    
Changes in goodwill    
Goodwill acquired through acquisition   1,347,000
U.S. Services    
Changes in goodwill    
Balance at the beginning of the period 164,472,000 139,588,000
Goodwill acquired through acquisition 0  
Other   0
Disposal of Q2 Administrators, LLC 0  
Foreign currency translation 0 0
Balance at the end of the period 164,472,000 164,472,000
U.S. Services | General Dynamics Information Technology's Citizen Engagement Centers    
Changes in goodwill    
Goodwill acquired through acquisition   24,884,000
U.S. Services | GT Hiring Solutions    
Changes in goodwill    
Goodwill acquired through acquisition   0
U.S. Federal Services    
Changes in goodwill    
Balance at the beginning of the period 382,618,000 228,148,000
Goodwill acquired through acquisition 0  
Other   0
Disposal of Q2 Administrators, LLC (899,000)  
Foreign currency translation 0 0
Balance at the end of the period 381,719,000 382,618,000
U.S. Federal Services | General Dynamics Information Technology's Citizen Engagement Centers    
Changes in goodwill    
Goodwill acquired through acquisition   154,470,000
U.S. Federal Services | GT Hiring Solutions    
Changes in goodwill    
Goodwill acquired through acquisition   0
Outside the U.S.    
Changes in goodwill    
Balance at the beginning of the period 37,379,000 32,146,000
Goodwill acquired through acquisition 7,652,000  
Other   372,000
Disposal of Q2 Administrators, LLC 0  
Foreign currency translation 1,907,000 (1,772,000)
Balance at the end of the period $ 46,938,000 37,379,000
Outside the U.S. | General Dynamics Information Technology's Citizen Engagement Centers    
Changes in goodwill    
Goodwill acquired through acquisition   5,286,000
Outside the U.S. | GT Hiring Solutions    
Changes in goodwill    
Goodwill acquired through acquisition   $ 1,347,000