Supplementary Data on Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Cash flows from operating activities:
Net income	$ 298,569	$ 297,860	$ 293,304
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	46,166	37,210	21,195
Deferred income tax expense (benefit)	9,468	(1,854)	(5,162)
Lease amortization expense	5,554	11,887	13,108
Losses (gains) and impairment losses (recoveries) on investments	27,953	(2,307)	(3,114)
Loss (gain) on disposal of fixed assets	172	(13)	(15)
Net investment loss (income)	12,916	(25,944)	5,878
(Decrease) increase in deferred compensation	(1,463)	(5,006)	7,611
(Increase) decrease in receivables from affiliates	(45,814)	15,514	(26,548)
Increase in accrued investment income	(1,998)	(157)	(713)
Increase in pension liability	15,647	52,755	41,227
(Increase) decrease in prepaid expenses and other assets	(25,843)	12,161	(4,771)
Increase (decrease) in accounts payable and accrued expenses	18,993	(4,823)	(14,307)
Increase (decrease) in commissions payable	29,282	8,408	(625)
(Decrease) increase in accrued agent bonuses	(25,271)	10,279	14,105
Increase (decrease) in contract liability	1,821	(3,176)	1,422
Net cash provided by operating activities	$ 366,152	$ 402,794	$ 342,595