Fair Value Measurements and Derivative Instruments (Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	$ 250,287	$ 260,145
Gross unrealized gains		11
Gross unrealized losses	(57,569)	(51,890)
Estimated fair value	192,718	208,266
Government and related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	35,125	35,744
Gross unrealized gains		11
Gross unrealized losses	(9,054)	(8,210)
Estimated fair value	26,071	27,545
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	65,271	66,300
Gross unrealized gains		0
Gross unrealized losses	(14,451)	(13,981)
Estimated fair value	50,820	52,319
Commingled fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	1,778	1,749
Gross unrealized gains		0
Gross unrealized losses	(278)	(229)
Estimated fair value	1,500	1,520
Mortgage-backed / asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	148,113	156,352
Gross unrealized gains		0
Gross unrealized losses	(33,786)	(29,470)
Estimated fair value	$ 114,327	$ 126,882