v3.26.1
Investments - Schedule of Fair Values and Gross Unrealized Gains and Losses (Details) - USD ($)
$ in Thousands
Jun. 30, 2026
Dec. 31, 2025
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 3,346,838 $ 3,190,174
Gross Unrealized, Gains 10,208 33,125
Gross Unrealized, Losses (99,106) (86,276)
Fair Value 3,257,940 3,137,023
U.S. Treasury securities and obligations of U.S. government agencies    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 219,938 306,168
Gross Unrealized, Gains 343 2,544
Gross Unrealized, Losses (5,481) (1,684)
Fair Value 214,800 307,028
Municipal debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 593,325 635,396
Gross Unrealized, Gains 760 3,052
Gross Unrealized, Losses (28,261) (26,879)
Fair Value 565,824 611,569
Corporate debt securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 2,251,283 2,047,122
Gross Unrealized, Gains 9,065 27,504
Gross Unrealized, Losses (61,801) (55,015)
Fair Value 2,198,547 2,019,611
U.S. agency mortgage-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 39,399 42,109
Gross Unrealized, Gains 0 10
Gross Unrealized, Losses (492) (48)
Fair Value $ 38,907 $ 42,071
U.S. agency mortgage-backed securities 100.00% 100.00%
Other asset-backed securities    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost $ 153,714 $ 72,774
Gross Unrealized, Gains 40 0
Gross Unrealized, Losses (3,033) (2,649)
Fair Value 150,721 70,125
Total bonds    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 3,257,659 3,103,569
Gross Unrealized, Gains 10,208 33,110
Gross Unrealized, Losses (99,068) (86,275)
Fair Value 3,168,799 3,050,404
Short-term investments    
Debt Securities, Available-for-sale [Line Items]    
Amortized Cost 89,179 86,605
Gross Unrealized, Gains 0 15
Gross Unrealized, Losses (38) (1)
Fair Value $ 89,141 $ 86,619