Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011
Operating activities
Net earnings	$ 283,139	$ 176,905
Adjustments to reconcile net earnings to net cash provided by operating activities
Change in premium, claims and other receivables	6,623	(76,927)
Change in reinsurance recoverables	47,149	(56,510)
Change in ceded unearned premium	(39,918)	47,477
Change in loss and loss adjustments expense payable	16,052	196,046
Change in unearned premium	87,177	24,655
Change in reinsurance, premium and claims payable, excluding restricted cash	(32,743)	(34,052)
Change in accounts payable and accrued liabilities	79,500	5,082
Stock-based compensation expense	10,361	10,017
Depreciation and amortization expense	13,919	13,214
Other, net	24,776	(17,948)
Cash provided by operating activities	496,035	287,959
Investing activities
Proceeds from sales of available for sale fixed maturity securities	293,969	494,532
Proceeds from sale of equity securities	7,145
Maturity or call of available for sale fixed maturity securities	504,583	318,558
Maturity or call of held to maturity fixed maturity securities	28,511	24,950
Cost of available for sale fixed maturity securities acquired	(1,056,909)	(1,243,124)
Cost of equity securities acquired	205,092
Cost of other investments acquired	0	(33,060)
Change in short-term investments	(5,401)	288,909
Payments for purchase of businesses, net of cash received	(32,590)	(1,892)
Other, net	(2,911)	(14,184)
Cash used by investing activities	(468,695)	(165,311)
Financing activities
Advances on line of credit	140,000	210,000
Payments on line of credit	(70,000)	(15,000)
Sale of common stock	40,105	36,245
Purchase of common stock	(135,151)	(303,311)
Dividends paid	(47,617)	(49,301)
Other, net	5,066	(6,001)
Cash used by financing activities	(67,597)	(127,368)
Net decrease in cash	(40,257)	(4,720)
Cash at beginning of year	104,550	97,857
Cash at end of period	$ 64,293	$ 93,137