Schedule II - Condensed Financial Information of Registrant (Parent Company) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Cash flows from operating activities:
Net earnings	$ 279,354	$ 157,091	$ 191,642
Adjustments to reconcile net losses to net cash provided by (used in) operating activities:
Net realized (gains) losses	(64,222)	(17,885)	(17,520)
Depreciation	7,394	7,432	8,164
Other items, net	14,141	10,460	25,341
Changes in investment in unconsolidated investees:
Undistributed earnings	(37,060)	(20,233)	(20,960)
Dividends received		4,675	13,200
Net cash provided by operating activities	384,905	263,259	276,917
Purchase of:
Fixed income securities, available-for-sale	(733,811)	(518,362)	(539,726)
Other	(11,428)	(12,851)	(22,751)
Sale of:
Fixed income securities, available-for-sale	63,811	84,587	196,558
Call or maturity of:
Fixed income, available-for-sale	376,750	283,107	201,383
Net cash used in investing activities	(274,826)	(167,987)	(184,753)
Cash flows from financing activities:
Proceeds from stock option exercises	1,838	8,648	9,490
Net cash used in financing activities	(83,492)	(79,258)	(76,101)
Net increase in cash	26,587	16,014	16,063
Cash at beginning of year	62,217	46,203	30,140
Cash at end of year	88,804	62,217	46,203
Parent Company
Cash flows from operating activities:
Net earnings	4,902	(2,702)	426
Adjustments to reconcile net losses to net cash provided by (used in) operating activities:
Net realized (gains) losses	625	(501)	(463)
Depreciation	68	67	68
Other items, net	3,966	2,270	2,487
Change in:
Affiliate balances receivable/payable	(3,404)	1,246	1,180
Federal income taxes	5,901	1,399	(1,673)
Changes in investment in unconsolidated investees:
Undistributed earnings	(22,786)	(10,368)	(13,592)
Dividends received			13,200
Net cash provided by operating activities	(10,728)	(8,589)	1,633
Purchase of:
Fixed income securities, available-for-sale	(33,373)	(24,950)	(2,507)
Other	(2,904)	(346)
Sale of:
Fixed income securities, available-for-sale	5,306	3,767	14,273
Other	1,245
Call or maturity of:
Fixed income, available-for-sale	2,878	3,492	29,501
Cash dividends received-subsidiaries	180,000	110,000	34,003
Net cash used in investing activities	153,152	91,963	75,270
Cash flows from financing activities:
Proceeds from stock option exercises	1,838	8,648	9,490
Cash dividends paid	(147,422)	(95,793)	(93,315)
Other	4,212	3,802	4,058
Net cash used in financing activities	(141,372)	(83,343)	(79,767)
Net increase in cash	1,052	31	(2,864)
Cash at beginning of year	381	350	3,214
Cash at end of year	$ 1,433	$ 381	$ 350