Investments - Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Amortized Cost
Less than 12 months		$ 1,045,120
12 months or greater		310,494
Amortized Cost		1,355,614
Fair Value
Less than 12 months		1,039,333
12 months or greater		293,610
Fair Value	$ 0	1,332,943
Accrued interest income	$ 0	$ 3,000