Fair Value Measurements and Derivative Instruments (Unrealized Holding Losses) (Details) - USD ($) $ in Thousands	Sep. 30, 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	$ 148,732	$ 157,979
Greater than 12 continuous months, Gross unrealized losses	31,259	38,944
Government securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	13,374	15,744
Greater than 12 continuous months, Gross unrealized losses	5,713	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	43,769	42,159
Greater than 12 continuous months, Gross unrealized losses	5,909	8,208
Mutual funds
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	1,695	1,612
Greater than 12 continuous months, Gross unrealized losses	178	223
Mortgage-backed securities
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Greater than 12 continuous months, Fair Value	89,894	90,628
Greater than 12 continuous months, Gross unrealized losses	19,459	24,313
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	0	7,836
Greater than 12 continuous months, Gross unrealized losses	$ 0	$ 512