v3.22.2.2
Fair Value Measurements - Assets Measured for at Fair Value on Recurring Basis (Detail) - USD ($)
$ in Thousands
Sep. 30, 2022
Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value $ 996,783 $ 1,040,455
Equity Securities: 82,387 47,334
U.S. government obligations and agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 11,598 26,806
Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 675,363 673,805
Mortgage-backed and asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 289,733 316,118
Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 12,438 14,574
Redeemable preferred stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 7,651 9,152
Fair Value, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets accounted for at fair value 1,079,170 1,087,789
Fair Value, Recurring | U.S. government obligations and agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 11,598 26,806
Fair Value, Recurring | Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 675,363 673,805
Fair Value, Recurring | Mortgage-backed and asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 289,733 316,118
Fair Value, Recurring | Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 12,438 14,574
Fair Value, Recurring | Redeemable preferred stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 7,651 9,152
Fair Value, Recurring | Common stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 19,746 3,683
Fair Value, Recurring | Mutual funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 62,641 43,651
Level 1 | Fair Value, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets accounted for at fair value 82,387 47,334
Level 1 | Fair Value, Recurring | U.S. government obligations and agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 1 | Fair Value, Recurring | Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 1 | Fair Value, Recurring | Mortgage-backed and asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 1 | Fair Value, Recurring | Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 1 | Fair Value, Recurring | Redeemable preferred stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 1 | Fair Value, Recurring | Common stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 19,746 3,683
Level 1 | Fair Value, Recurring | Mutual funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 62,641 43,651
Level 2 | Fair Value, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets accounted for at fair value 996,783 1,040,455
Level 2 | Fair Value, Recurring | U.S. government obligations and agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 11,598 26,806
Level 2 | Fair Value, Recurring | Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 675,363 673,805
Level 2 | Fair Value, Recurring | Mortgage-backed and asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 289,733 316,118
Level 2 | Fair Value, Recurring | Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 12,438 14,574
Level 2 | Fair Value, Recurring | Redeemable preferred stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 7,651 9,152
Level 2 | Fair Value, Recurring | Common stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 0 0
Level 2 | Fair Value, Recurring | Mutual funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 0 0
Level 3 | Fair Value, Recurring    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Total assets accounted for at fair value 0 0
Level 3 | Fair Value, Recurring | U.S. government obligations and agencies    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 3 | Fair Value, Recurring | Corporate bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 3 | Fair Value, Recurring | Mortgage-backed and asset-backed securities    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 3 | Fair Value, Recurring | Municipal bonds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 3 | Fair Value, Recurring | Redeemable preferred stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Fair Value 0 0
Level 3 | Fair Value, Recurring | Common stock    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: 0 0
Level 3 | Fair Value, Recurring | Mutual funds    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Equity Securities: $ 0 $ 0