Schedule II - Condensed Financial Information of Registrant Cash Flow (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net earnings	$ 21,776	$ 35,641	$ 32,466	$ 26,875	$ 39,587	$ 21,813	$ 25,483	$ 23,538	$ 116,758	$ 110,421	$ 100,892
Adjustments to reconcile net earnings/(loss) to cash provided by operating activities:
Depreciation and amortization									11,825	10,005	8,057
Change in:
Federal income tax, net									(20,635)	1,912	13,301
Deferred Federal income tax									26,438	(40,227)	10,152
Other, net									(12,728)	27,456	7,925
Net cash provided by operating activities									326,623	276,130	309,143
Cash flows from financing activities:
Dividends on common stock									(1,273)	(1,273)	(1,273)
Net cash provided by (used in) financing activities									(441,914)	(164,535)	(54,087)
Net increase (decrease) in cash and cash equivalents									(85,648)	166,377	(54,760)
Cash and cash equivalents at beginning of year				217,624				51,247	217,624	51,247	106,007
Cash and cash equivalents at end of year	131,976				217,624				131,976	217,624	51,247
The Company
Cash flows from operating activities:
Net earnings									116,758	110,421	100,892
Adjustments to reconcile net earnings/(loss) to cash provided by operating activities:
Equity in earnings/(loss) of affiliates									(112,701)	(106,125)	(100,846)
Depreciation and amortization									30	30	30
Change in:
Federal income tax, net									(1,166)	(1,843)	(1,008)
Deferred Federal income tax									448	348	(530)
Due to subsidiaries, net									0	(608)	608
Other, net									(1,956)	(917)	1,896
Net cash provided by operating activities									1,413	1,306	1,042
Cash flows from financing activities:
Dividends on common stock									(1,273)	(1,273)	(1,273)
Net cash provided by (used in) financing activities									(1,273)	(1,273)	(1,273)
Net increase (decrease) in cash and cash equivalents									140	33	(231)
Cash and cash equivalents at beginning of year				$ 1,303				$ 1,270	1,303	1,270	1,501
Cash and cash equivalents at end of year	$ 1,443				$ 1,303				$ 1,443	$ 1,303	$ 1,270