Investments - Maturity Table (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	$ 2,713,795	$ 2,535,568
Estimated Fair Value	2,566,556	$ 2,517,956
2022
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	168,911
Estimated Fair Value	167,988
2023
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	162,572
Estimated Fair Value	158,500
2024
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	697,203
Estimated Fair Value	671,600
2025
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	297,323
Estimated Fair Value	289,516
2026
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	547,952
Estimated Fair Value	502,996
2027
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	98,007
Estimated Fair Value	98,111
2038
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	73
Estimated Fair Value	76
2039
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	858
Estimated Fair Value	875
2042
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,869
Estimated Fair Value	2,605
2043
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	4,890
Estimated Fair Value	4,626
2044
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	6,003
Estimated Fair Value	5,766
2045
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	5,761
Estimated Fair Value	5,409
2046
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	8,740
Estimated Fair Value	8,138
2047
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	9,848
Estimated Fair Value	9,394
2048
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	2,423
Estimated Fair Value	2,373
2049
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	17,158
Estimated Fair Value	16,122
2050
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	122,356
Estimated Fair Value	104,863
2051
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	169,687
Estimated Fair Value	144,802
2052
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	59,129
Estimated Fair Value	54,486
2053
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	124,157
Estimated Fair Value	116,111
2054
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	97,235
Estimated Fair Value	91,559
2055
Debt Securities, Available-for-sale [Line Items]
Amortized Cost	110,640
Estimated Fair Value	$ 110,640