Investments - Maturity Table (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,423,183	$ 2,563,984
Estimated Fair Value	2,271,108	$ 2,411,622
2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	449,757
Estimated Fair Value	442,325
2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	299,063
Estimated Fair Value	290,830
2026
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	548,807
Estimated Fair Value	504,757
2027
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	98,713
Estimated Fair Value	94,816
2038
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	68
Estimated Fair Value	68
2039
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	581
Estimated Fair Value	566
2042
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,252
Estimated Fair Value	1,928
2043
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,079
Estimated Fair Value	3,626
2044
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,467
Estimated Fair Value	4,047
2045
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,898
Estimated Fair Value	4,300
2046
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,451
Estimated Fair Value	6,498
2047
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,409
Estimated Fair Value	6,533
2048
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,008
Estimated Fair Value	1,923
2049
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	15,238
Estimated Fair Value	13,344
2050
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	106,282
Estimated Fair Value	83,558
2051
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	153,057
Estimated Fair Value	119,243
2052
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	51,825
Estimated Fair Value	44,160
2053
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	242,958
Estimated Fair Value	235,101
2054
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	86,866
Estimated Fair Value	79,516
2055
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	82,255
Estimated Fair Value	79,089
2056
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	210,422
Estimated Fair Value	209,947
2058
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	44,727
Estimated Fair Value	$ 44,933