Contract Revenue and Pass-through and Other Revenue - Schedule of Deferred Revenue Remaining Performance Obligations (Detail) $ in Thousands	Sep. 30, 2023 USD ($)
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 21,047
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2023-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 4,880
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 5,281
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2025-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 4,199
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2026-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 3,835
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2027-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 2,008
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2028-10-01
Revenue Remaining Performance Obligation Expected Timing Of Satisfaction [Line Items]
Total Revenue	$ 844
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year