Supplemental Stockholders' Equity Information - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	$ 1,804,986	$ 1,607,220	$ 1,763,219	$ 1,599,972
Other comprehensive income before reclassifications, before tax			5,130
Amounts reclassified from accumulated other comprehensive loss, before tax			9,890
Income tax expense			3,969
Net current-period other comprehensive income, net of tax	8,501	813	11,051	6,978
Balance, end of period	1,852,052	1,655,240	1,852,052	1,655,240
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			910
Other comprehensive income before reclassifications, before tax			241
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax expense			64
Net current-period other comprehensive income, net of tax			177
Balance, end of period	1,087		1,087
Funded Status of Benefit Plans
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(353,286)
Other comprehensive income before reclassifications, before tax			0
Amounts reclassified from accumulated other comprehensive loss, before tax			9,890
Income tax expense			2,625
Net current-period other comprehensive income, net of tax			7,265
Balance, end of period	(346,021)		(346,021)
Net Unrealized Gain/(Loss) on Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period			(486)
Other comprehensive income before reclassifications, before tax			4,889
Amounts reclassified from accumulated other comprehensive loss, before tax			0
Income tax expense			1,280
Net current-period other comprehensive income, net of tax			3,609
Balance, end of period	3,123		3,123
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Balance, beginning of period	(350,312)	(351,682)	(352,862)	(357,847)
Net current-period other comprehensive income, net of tax	8,501	813	11,051	6,978
Balance, end of period	$ (341,811)	$ (350,869)	$ (341,811)	$ (350,869)