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Fair Value Measurement - Summary of Investments Measured at Fair Value on Recurring Basis (Detail) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023
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Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | $ 325,163 | $ 368,753
Gross Unrealized Gains | 48 | 51
Gross Unrealized Losses | (26,648) | (28,802)
Recorded Basis | 298,563 | 340,002
Cash and Cash Equivalents [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 26,661 | 19,539
Recorded Basis | 26,661 | 19,539
Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 72,886 | 88,496
Gross Unrealized Gains | 15 | 6
Gross Unrealized Losses | (6,409) | (7,475)
Recorded Basis | 66,492 | 81,027
Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 225,616 | 260,718
Gross Unrealized Gains | 33 | 45
Gross Unrealized Losses | (20,239) | (21,327)
Recorded Basis | 205,410 | 239,436
Money Market Funds [Member] | Cash and Cash Equivalents [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 26,661 | 19,539
Recorded Basis | 26,661 | 19,539
Money Market Funds [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 216 | 337
Recorded Basis | 216 | 337
Corporate Bonds [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 27,954 | 34,472
Gross Unrealized Gains | 3 | 2
Gross Unrealized Losses | (2,365) | (3,161)
Recorded Basis | 25,592 | 31,313
Corporate Bonds [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 100,030 | 82,481
Gross Unrealized Gains | 16 | 19
Gross Unrealized Losses | (7,302) | (8,473)
Recorded Basis | 92,744 | 74,027
U.S. Government Agency Securities [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 12,734 | 12,830
Gross Unrealized Losses | (203) | (408)
Recorded Basis | 12,531 | 12,422
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 | 16,785 | 16,863
Gross Unrealized Losses | (914) | (1,199)
Recorded Basis | 15,871 | 15,664
U.S. Treasuries [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 12,460 | 12,448
Gross Unrealized Losses | (1,140) | (1,253)
Recorded Basis | 11,320 | 11,195
U.S. Treasuries [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 54,900 | 109,020
Gross Unrealized Gains |  | 21
Gross Unrealized Losses | (6,348) | (6,436)
Recorded Basis | 48,552 | 102,605
Mortgage-Backed Securities [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 12,128 | 13,084
Gross Unrealized Losses | (2,592) | (2,454)
Recorded Basis | 9,536 | 10,630
Mortgage-Backed Securities [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 40,858 | 42,077
Gross Unrealized Gains | 10 | 2
Gross Unrealized Losses | (5,674) | (5,218)
Recorded Basis | 35,194 | 36,861
Asset-Backed Securities [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 7,610 | 13,659
Gross Unrealized Gains | 12 | 4
Gross Unrealized Losses | (109) | (191)
Recorded Basis | 7,513 | 13,472
Asset-Backed Securities [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 1,666 | 799
Gross Unrealized Gains | 6 | 1
Gross Unrealized Losses | (1) | (1)
Recorded Basis | 1,671 | 799
Emerging Markets [Member] | Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost |  | 2,003
Gross Unrealized Losses |  | (8)
Recorded Basis |  | 1,995
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 | 1 | 2
Recorded Basis | 201 | 202
Mutual Funds [Member] | Restricted Cash and Investments [Member] |  |
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items] |  |
Cost | 10,961 | 8,941
Recorded Basis | $ 10,961 | $ 8,941

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