Investments - Maturity Table (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,643,540	$ 2,535,568
Estimated Fair Value	2,427,540	$ 2,517,956
2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	124,994
Estimated Fair Value	124,744
2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	162,549
Estimated Fair Value	157,988
2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	697,586
Estimated Fair Value	660,951
2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	297,572
Estimated Fair Value	282,163
2026
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	548,076
Estimated Fair Value	484,902
2027
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	98,109
Estimated Fair Value	93,900
2038
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	72
Estimated Fair Value	73
2039
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	831
Estimated Fair Value	810
2042
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,742
Estimated Fair Value	2,347
2043
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,834
Estimated Fair Value	4,285
2044
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,597
Estimated Fair Value	5,047
2045
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,699
Estimated Fair Value	5,002
2046
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,170
Estimated Fair Value	7,138
2047
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,718
Estimated Fair Value	7,750
2048
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,154
Estimated Fair Value	2,050
2049
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	16,820
Estimated Fair Value	14,799
2050
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	119,167
Estimated Fair Value	95,297
2051
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	165,761
Estimated Fair Value	131,838
2052
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	57,773
Estimated Fair Value	49,940
2053
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	117,467
Estimated Fair Value	107,891
2054
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	92,527
Estimated Fair Value	85,057
2055
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	106,322
Estimated Fair Value	$ 103,568