Fair Value Measurements and Derivative Instruments (Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	$ 273,840	$ 282,350
Gross unrealized gains	121	484
Gross unrealized losses	(28,707)	(8,728)
Estimated fair value	245,254	274,106
Government and related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	35,987	36,160
Gross unrealized gains	57	81
Gross unrealized losses	(5,065)	(1,012)
Estimated fair value	30,979	35,229
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	67,599	67,906
Gross unrealized gains	46	259
Gross unrealized losses	(8,048)	(2,998)
Estimated fair value	59,597	65,167
Commingled fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	1,730	1,725
Gross unrealized gains	0	0
Gross unrealized losses	(112)	(33)
Estimated fair value	1,618	1,692
Mortgage-backed / asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	168,524	176,559
Gross unrealized gains	18	144
Gross unrealized losses	(15,482)	(4,685)
Estimated fair value	$ 153,060	$ 172,018