Fair Value Measurements and Derivative Instruments (Unrealized Holding Losses) (Details) - USD ($) $ in Thousands	Mar. 31, 2025	Dec. 31, 2024
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	$ 151,612	$ 154,053
Greater than 12 continuous months, Gross unrealized losses	35,013	38,719
Less than 12 continuous months, Fair Value	113	3,926
Less than 12 continuous months, Gross unrealized losses	1	225
Government and related securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	15,478	15,744
Greater than 12 continuous months, Gross unrealized losses	5,937	5,688
Corporate debt securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	42,912	39,845
Greater than 12 continuous months, Gross unrealized losses	7,258	8,206
Less than 12 continuous months, Fair Value	0	2,314
Less than 12 continuous months, Gross unrealized losses	0	2
Commingled fixed income securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	1,646	0
Greater than 12 continuous months, Gross unrealized losses	201	0
Less than 12 continuous months, Fair Value	0	1,612
Less than 12 continuous months, Gross unrealized losses	0	223
Mortgage-backed / asset-backed securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	91,576	98,464
Greater than 12 continuous months, Gross unrealized losses	21,617	24,825
Less than 12 continuous months, Fair Value	113	0
Less than 12 continuous months, Gross unrealized losses	$ 1	$ 0

Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for more than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of accumulated unrealized loss on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for 12 months or longer, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale), in continuous unrealized loss position for less than 12 months, without allowance for credit loss. Includes beneficial interest in securitized financial asset.

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