SCHEDULE II-CONDENSED FINANCIAL INFORMATION OF REGISTRANT (PARENT COMPANY) - Statements of Earnings and Comprehensive Earnings (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CONDENSED STATEMENTS OF EARNINGS AND COMPREHENSIVE EARNINGS
Net investment income	$ 13,153	$ 13,504	$ 13,048	$ 13,370	$ 13,754	$ 13,964	$ 13,431	$ 13,495	$ 53,075	$ 54,644	$ 55,608
Net realized gains (losses)	11,283	9,252	2,710	11,400	14,207	7,534	4,802	13,286	34,645	39,829	32,182
Equity in earnings of unconsolidated investees									10,833	10,914	12,338
Interest expense on debt									(7,426)	(7,426)	(7,438)
Loss before income taxes	38,006	31,142	42,341	45,593	45,582	51,937	54,650	44,513	157,082	196,682	189,487
Income tax benefit									42,162	59,138	54,042
Net earnings	$ 32,187	$ 22,263	$ 29,077	$ 31,393	$ 33,853	$ 35,908	$ 37,185	$ 30,598	114,920	137,544	135,445
Unrealized gains (losses) on securities:
Other comprehensive earnings (loss), net of tax									(1,164)	(47,609)	35,356
Comprehensive earnings									113,756	89,935	170,801
PARENT COMPANY
CONDENSED STATEMENTS OF EARNINGS AND COMPREHENSIVE EARNINGS
Net investment income									942	810	663
Net realized gains (losses)									(360)	139	271
Equity in earnings of unconsolidated investees									9,764	9,893	12,009
Selling, general and administrative expenses									(10,170)	(9,837)	(10,222)
Interest expense on debt									(7,426)	(7,426)	(7,438)
Loss before income taxes									(7,250)	(6,421)	(4,717)
Income tax benefit									(8,467)	(5,499)	(7,959)
Net earnings (loss) before equity in net earnings of subsidiaries									1,217	(922)	3,242
Equity in net earnings of subsidiaries									113,703	138,466	132,203
Net earnings									114,920	137,544	135,445
Unrealized gains (losses) on securities:
Unrealized holding gains (losses) arising during the period									308	(40)	372
Less: reclassification adjustment for losses (gains) included in net earnings									(131)	(90)	(176)
Other Comprehensive Income (Loss), Net of Tax, Total									177	(130)	196
Equity in other comprehensive earnings (loss) of subsidiaries/investees									(1,341)	(47,479)	35,160
Other comprehensive earnings (loss), net of tax									(1,164)	(47,609)	35,356
Comprehensive earnings									$ 113,756	$ 89,935	$ 170,801