Summary of Significant Accounting Policies (Changes in AOCI Balances by Component) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	$ 1,449,718
Balance at the beginning of the period, noncontrolling interests	(7,734)
Other comprehensive income (loss) before reclassifications	5,912	$ (5,357)	$ 1,330
Amounts reclassified from AOCI	1,338	1,955	1,776
Other comprehensive income	999	(2,272)	140
Balance at the end of the period	1,291,588	1,449,718
Balance at the end of the period, noncontrolling interests	(7,677)	(7,734)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(47,037)	(43,635)	(46,741)
Balance at the end of the period	(39,787)	(47,037)	(43,635)
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(32,637)	(37,866)	(44,087)
Other comprehensive income (loss) before reclassifications	2,036	3,370	4,167
Amounts reclassified from AOCI	1,247	1,859	2,054
Balance at the end of the period	(29,354)	(32,637)	(37,866)
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(7,241)	(5,787)	(5,322)
Other comprehensive income (loss) before reclassifications	348	(1,454)	(465)
Amounts reclassified from AOCI	0	0	0
Balance at the end of the period	(6,893)	(7,241)	(5,787)
Unrealized Gain (Loss) in Fair Value of Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period	(7,159)	18	2,668
Other comprehensive income (loss) before reclassifications	3,528	(7,273)	(2,372)
Amounts reclassified from AOCI	91	96	(278)
Balance at the end of the period	(3,540)	(7,159)	18
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period, noncontrolling interests	(1,730)	542	402
Balance at the end of the period, noncontrolling interests	(731)	(1,730)	542
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period, noncontrolling interests	0	0	0
Other comprehensive income	0	0	0
Balance at the end of the period, noncontrolling interests	0	0	0
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period, noncontrolling interests	(799)	542	402
Other comprehensive income	487	(1,341)	140
Balance at the end of the period, noncontrolling interests	(312)	(799)	542
Unrealized Gain (Loss) in Fair Value of Investments
Accumulated Other Comprehensive Income (Loss) [Line Items]
Balance at the beginning of the period, noncontrolling interests	(931)	0	0
Other comprehensive income	512	(931)	0
Balance at the end of the period, noncontrolling interests	$ (419)	$ (931)	$ 0