Marketable Securities - Held to Maturity, by Contractual Maturity (Details) - Mortgage-backed securities $ in Thousands	Mar. 31, 2026 USD ($)
Amortized cost
Due after one year through five years	$ 31,700
Due after five years through ten years	67,553
Due after ten years	439,419
Amortized cost	538,672
Fair value
Due after one year through five years	28,616
Due after five years through ten years	60,492
Due after ten years	378,621
Total mortgage-backed securities	$ 467,729

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