Condensed Consolidated Statements of Earnings and Comprehensive Earnings (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Net premiums earned	$ 141,584	$ 130,826	$ 278,864	$ 246,877
Net investment income	14,826	15,180	30,119	31,483
Net realized investment gains	492	10,050	11,908	14,522
Other-than-temporary impairment (OTTI) losses on investments	(1,156)		(1,156)
Consolidated revenue	155,746	156,056	319,735	292,882
Losses and settlement expenses	61,005	30,363	122,888	77,234
Policy acquisition costs	48,173	46,243	96,370	84,861
Insurance operating expenses	10,783	12,130	23,042	21,745
Interest expense on debt	1,525	1,512	3,025	3,024
General corporate expenses	1,815	1,964	3,802	3,969
Total expenses	123,301	92,212	249,127	190,833
Equity in earnings of unconsolidated investee	4,123	3,886	7,069	6,502
Earnings before income taxes	36,568	67,730	77,677	108,551
Income tax expense	11,820	22,738	24,891	35,853
Net earnings	24,748	44,992	52,786	72,698
Unrealized gains (losses) on securities:
Unrealized holding gains arising during the period	5,430	9,224	24,939	17,378
Less: Reclassification adjustment for losses (gains) included in net earnings	460	(6,464)	(8,273)	(9,370)
Other comprehensive earnings	5,890	2,760	16,666	8,008
Comprehensive earnings	$ 30,638	$ 47,752	$ 69,452	$ 80,706
Basic:
Basic net earnings per share (in dollars per share)	$ 1.17	$ 2.13	$ 2.49	$ 3.45
Basic comprehensive earnings per share (in dollars per share)	$ 1.44	$ 2.27	$ 3.28	$ 3.83
Diluted:
Diluted net earnings per share (in dollars per share)	$ 1.15	$ 2.11	$ 2.45	$ 3.41
Diluted comprehensive earnings per share (in dollars per share)	$ 1.42	$ 2.24	$ 3.23	$ 3.79
Weighted average number of common shares outstanding
Basic (in shares)	21,213	21,075	21,200	21,050
Diluted (in shares)	21,514	21,332	21,521	21,315
Cash dividends declared per common share (in dollars per share)	$ 0.32	$ 0.30	$ 0.62	$ 0.59