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Fair Value Measurement - Summary of Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2025
Dec. 31, 2024
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost $ 282,435 $ 325,163
Gross Unrealized Gains 215 48
Gross Unrealized Losses (17,606) (26,648)
Recorded Basis 265,044 298,563
Cash and Cash Equivalents [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 22,304 26,661
Recorded Basis 22,304 26,661
Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 66,462 72,886
Gross Unrealized Gains 20 15
Gross Unrealized Losses (4,406) (6,409)
Recorded Basis 62,076 66,492
Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 193,669 225,616
Gross Unrealized Gains 195 33
Gross Unrealized Losses (13,200) (20,239)
Recorded Basis 180,664 205,410
Money Market Funds [Member] | Cash and Cash Equivalents [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 22,304 26,661
Recorded Basis 22,304 26,661
Money Market Funds [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 1,305 216
Recorded Basis 1,305 216
Corporate Bonds [Member] | Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 27,874 27,954
Gross Unrealized Gains 5 3
Gross Unrealized Losses (1,402) (2,365)
Recorded Basis 26,477 25,592
Corporate Bonds [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 81,386 100,030
Gross Unrealized Gains 70 16
Gross Unrealized Losses (4,403) (7,302)
Recorded Basis 77,053 92,744
U.S. Treasuries [Member] | Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 14,260 12,460
Gross Unrealized Losses (744) (1,140)
Recorded Basis 13,516 11,320
U.S. Treasuries [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 52,535 54,900
Gross Unrealized Gains 14  
Gross Unrealized Losses (4,144) (6,348)
Recorded Basis 48,405 48,552
Mortgage-Backed Securities [Member] | Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 11,426 12,128
Gross Unrealized Losses (2,132) (2,592)
Recorded Basis 9,294 9,536
Mortgage-Backed Securities [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 37,884 40,858
Gross Unrealized Gains 87 10
Gross Unrealized Losses (4,280) (5,674)
Recorded Basis 33,691 35,194
Asset-Backed Securities [Member] | Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 7,572 7,610
Gross Unrealized Gains 15 12
Gross Unrealized Losses (64) (109)
Recorded Basis 7,523 7,513
Asset-Backed Securities [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 1,401 1,666
Gross Unrealized Gains 14 6
Gross Unrealized Losses   (1)
Recorded Basis 1,415 1,671
Mutual Funds [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 13,003 10,961
Recorded Basis 13,003 10,961
U.S. Government Agency Securities [Member] | Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 5,330 12,734
Gross Unrealized Losses (64) (203)
Recorded Basis 5,266 12,531
U.S. Government Agency Securities [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 5,955 16,785
Gross Unrealized Losses (373) (914)
Recorded Basis 5,582 15,871
Emerging Markets [Member] | Restricted Cash and Investments [Member]    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Cost 200 200
Gross Unrealized Gains 10 1
Recorded Basis $ 210 $ 201