Consolidated Statements of Cash Flows - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash flows from operating activities:
Net earnings	$ 105,028,000	$ 114,920,000	$ 137,544,000
Adjustments to reconcile net earnings to net cash provided by operating activities
Net realized gains	(4,411,000)	(34,645,000)	(39,829,000)
Depreciation	6,944,000	6,430,000	5,406,000
Other items, net	16,368,000	17,699,000	15,006,000
Change in:
Accrued investment income	(573,000)	285,000	(249,000)
Premiums and reinsurance balances receivable (net of direct write-offs and commutations)	(7,964,000)	17,275,000	10,911,000
Reinsurance balances payable	3,696,000	(19,628,000)	(457,000)
Funds held	1,818,000	18,488,000	2,773,000
Ceded unearned premium	(5,755,000)	660,000	1,128,000
Reinsurance balances recoverable on unpaid losses	(13,767,000)	9,620,000	37,262,000
Deferred policy acquisition costs	(4,569,000)	(3,318,000)	(4,706,000)
Accrued expenses	856,000	(3,750,000)	(7,406,000)
Unpaid losses and settlement expenses	132,166,000	35,552,000	(17,255,000)
Unearned premiums	17,672,000	11,683,000	20,682,000
Income taxes
Current	(3,019,000)	12,573,000	7,069,000
Deferred	(29,741,000)	1,128,000	7,034,000
Stock option excess tax benefit		(9,576,000)	(11,413,000)
Changes in investment in unconsolidated investees:
Undistributed earnings	(17,224,000)	(10,833,000)	(10,914,000)
Dividends received	0	9,900,000	0
Net Cash Provided by (Used in) Operating Activities, Total	197,525,000	174,463,000	152,586,000
Purchase of:
Fixed income, available-for-sale	(430,727,000)	(557,067,000)	(665,422,000)
Equity securities, available-for-sale	(20,719,000)	(36,335,000)	(39,905,000)
Short-term investments, net	(4,965,000)
Property and equipment	(9,238,000)	(16,155,000)	(10,035,000)
Investment in equity method investee			(1,711,000)
Acquisition of agency		(850,000)
Other	(19,112,000)	(7,722,000)	(4,642,000)
Proceeds from sale of:
Fixed income, available-for-sale	168,760,000	329,091,000	436,680,000
Equity securities, available-for-sale	36,573,000	89,909,000	53,110,000
Short-term investments, net		2,564,000	6,637,000
Property and equipment	128,000	1,688,000	76,000
Subsidiary or agency	408,000		7,500,000
Other	2,063,000		135,000
Proceeds from call or maturity of:
Fixed income, available-for-sale	195,617,000	141,255,000	156,980,000
Net Cash Provided by (Used in) Investing Activities, Total	(81,212,000)	(53,622,000)	(60,597,000)
Cash Flows from Financing Activities
Stock option excess tax benefit		9,576,000	11,413,000
Proceeds from stock option exercises	3,502,000	(741,000)	(3,364,000)
Cash dividends paid	(113,813,000)	(122,488,000)	(119,577,000)
Net Cash Used in Financing Activities, Total	(110,311,000)	(113,653,000)	(111,528,000)
Net increase (decrease) in cash	6,002,000	7,188,000	(19,539,000)
Cash at the beginning of the period	18,269,000	11,081,000	30,620,000
Cash at the end of the period	$ 24,271,000	$ 18,269,000	$ 11,081,000