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Investments - Breakdown of Investments with Unrealized Losses (Detail) - USD ($) $ in Thousands | Dec. 31, 2019 | Dec. 31, 2018
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Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | $ 8,965 | $ 21,135
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses | (19) | (123)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value | 136 | 8,456
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses | (2) | (147)
Total Fair Value | 9,101 | 29,591
Total Unrealized Losses | (21) | (270)
Corporate Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 203 | 11,129
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses |  | (60)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value |  | 3,608
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses |  | (52)
Total Fair Value | 203 | 14,737
Total Unrealized Losses |  | (112)
Municipal Fixed-Rate Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 930 |
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value |  | 1,136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses |  | (26)
Total Fair Value | 930 | 1,136
Total Unrealized Losses |  | (26)
Asset-Backed Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 797 | 1,874
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses | (3) | (2)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value |  | 1,257
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses |  | (12)
Total Fair Value | 797 | 3,131
Total Unrealized Losses | (3) | (14)
Mortgage/Agency-Backed Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 2,594 | 1,021
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses | (6) | (5)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value | 136 | 1,918
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses | (2) | (39)
Total Fair Value | 2,730 | 2,939
Total Unrealized Losses | (8) | (44)
U.S. Government Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 4,070 | 6,527
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses | (9) | (48)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value |  | 537
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses |  | (18)
Total Fair Value | 4,070 | 7,064
Total Unrealized Losses | (9) | (66)
Marketable Equity Securities [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value | 371 |
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses | (1) |
Total Fair Value | 371 |
Total Unrealized Losses | $ (1) |
Foreign Government Bonds [Member] |  |
Schedule of Available-for-sale Securities [Line Items] |  |
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value |  | 584
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses |  | (8)
Total Fair Value |  | 584
Total Unrealized Losses |  | $ (8)

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