Investments - Maturity Table (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,563,816	$ 2,554,332
Estimated Fair Value	2,372,846	$ 2,342,089
2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	65,001
Estimated Fair Value	64,075
2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	698,726
Estimated Fair Value	670,849
2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	298,314
Estimated Fair Value	283,644
2026
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	548,440
Estimated Fair Value	493,250
2027
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	98,409
Estimated Fair Value	93,990
2038
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	70
Estimated Fair Value	71
2039
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	693
Estimated Fair Value	681
2042
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,483
Estimated Fair Value	2,148
2043
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,263
Estimated Fair Value	3,830
2044
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,357
Estimated Fair Value	4,906
2045
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,254
Estimated Fair Value	4,678
2046
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	7,902
Estimated Fair Value	6,965
2047
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,311
Estimated Fair Value	7,331
2048
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,051
Estimated Fair Value	1,949
2049
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,013
Estimated Fair Value	14,251
2050
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	112,190
Estimated Fair Value	90,329
2051
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	158,214
Estimated Fair Value	126,858
2052
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	55,191
Estimated Fair Value	48,119
2053
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	143,586
Estimated Fair Value	133,023
2054
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	79,538
Estimated Fair Value	72,081
2055
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	94,046
Estimated Fair Value	90,092
2056
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	109,203
Estimated Fair Value	109,203
2058
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	50,561
Estimated Fair Value	$ 50,523