Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Operating activities
Net earnings	$ 391,240	$ 255,243	$ 345,096
Adjustments to reconcile net earnings to net cash provided by operating activities
Change in premium, claims and other receivables	61,675	(81,578)	(38,507)
Change in reinsurance recoverables	(6,812)	(47,892)	(2,077)
Change in ceded unearned premium	(34,580)	55,741	(10,713)
Change in loss and loss adjustments expense payable	82,201	181,363	6,702
Change in unearned premium	38,662	(14,364)	7,106
Change in reinsurance, premium and claims payable, excluding restricted cash	(59,177)	12,768	21,852
Change in accounts payable and accrued liabilities	100,091	17,538	31,032
Stock-based compensation expense	12,088	13,000	13,018
Depreciation and amortization expense	19,476	18,619	17,380
Gain on investments	(30,120)	1,026	(12,168)
Other, net	86,403	9,812	36,479
Cash provided by operating activities	661,147	421,276	415,200
Investing activities
Sales of available for sale fixed maturity securities	639,834	448,766	239,414
Sales of equity securities	14,117	0	0
Maturity or call of available for sale fixed maturity securities	697,404	573,958	620,884
Maturity or call of held to maturity fixed maturity securities	28,527	29,102	25,240
Cost of available for sale fixed maturity securities acquired	(1,489,235)	(1,550,587)	(1,347,285)
Cost of equity securities acquired	(262,528)	0	0
Cost of held to maturity fixed maturity securities acquired	0	0	(120,643)
Cost of other investments acquired	0	(33,060)	(4,977)
Change in short-term investments	(207,403)	355,468	311,983
Proceeds from sale of strategic and other investments	21,736	347	4,638
Payments for purchase of businesses, net of cash received	(46,627)	(1,892)	(36,348)
Proceeds from sale of subsidiaries	2,029	2,550	17,068
Other, net	(16,757)	(21,643)	(9,627)
Cash used by investing activities	(618,903)	(196,991)	(299,653)
Financing activities
Issuance of notes payable	0	0	0
Advances on line of credit	185,000	305,000	50,000
Payments on line of credit	(80,000)	(125,000)	(50,000)
Payments on convertible notes	0	0	(64,472)
Sale of common stock	59,838	36,044	29,193
Purchase of common stock	(173,028)	(373,584)	(35,124)
Dividends paid	(64,345)	(65,822)	(63,245)
Other, net	(2,869)	5,770	(13,502)
Cash used by financing activities	(75,404)	(217,592)	(147,150)
Net decrease in cash	(33,160)	6,693	(31,603)
Cash at beginning of year	104,550	97,857	129,460
Cash at end of period	$ 71,390	$ 104,550	$ 97,857