Fair Value Measurements and Derivative Instruments (Available-for-sale Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	$ 268,312	$ 282,350
Gross unrealized gains	33	484
Gross unrealized losses	(43,091)	(8,728)
Estimated fair value	225,254	274,106
Government and related securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	35,921	36,160
Gross unrealized gains	30	81
Gross unrealized losses	(7,063)	(1,012)
Estimated fair value	28,888	35,229
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	67,129	67,906
Gross unrealized gains	1	259
Gross unrealized losses	(12,447)	(2,998)
Estimated fair value	54,683	65,167
Commingled fixed income securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	1,735	1,725
Gross unrealized gains	0	0
Gross unrealized losses	(166)	(33)
Estimated fair value	1,569	1,692
Mortgage-backed / asset-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amortized cost	163,527	176,559
Gross unrealized gains	2	144
Gross unrealized losses	(23,415)	(4,685)
Estimated fair value	$ 140,114	$ 172,018