Consolidated Statements of Cash Flows (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Operating activities
Net earnings	$ 255,243,000	$ 345,096,000	$ 353,868,000
Adjustments to reconcile net earnings to net cash provided by operating activities
Change in premium, claims and other receivables	(81,578,000)	(38,507,000)	23,432,000
Change in reinsurance recoverables	(47,892,000)	(2,077,000)	42,521,000
Change in ceded unearned premium	55,741,000	(10,713,000)	(34,107,000)
Change in loss and loss adjustments expense payable	181,363,000	6,702,000	22,439,000
Change in unearned premium	(14,364,000)	7,106,000	48,366,000
Change in reinsurance, premium and claims payable, excluding restricted cash	12,768,000	21,852,000	(38,618,000)
Change in accounts payable and accrued liabilities	17,538,000	31,032,000	96,040,000
Stock-based compensation expense	13,000,000	13,018,000	15,628,000
Depreciation and amortization expense	18,619,000	17,380,000	16,221,000
Gain on investments	1,026,000	(12,168,000)	(3,518,000)
Other, net	9,812,000	36,479,000	40,525,000
Cash provided by operating activities	421,276,000	415,200,000	582,797,000
Investing activities
Proceeds from sales of available for sale fixed income securities	448,766,000	239,414,000	551,760,000
Maturity or call of available for sale fixed income securities	573,958,000	620,884,000	347,794,000
Maturity or call of held to maturity fixed income securities	29,102,000	25,240,000	86,364,000
Cost of available for sale fixed income securities acquired	(1,550,587,000)	(1,347,285,000)	(1,159,796,000)
Cost of held to maturity fixed income securities acquired	0	(120,643,000)	(59,754,000)
Cost of other investments acquired	(33,060,000)	(4,977,000)	0
Change in short-term investments	355,468,000	311,983,000	(297,016,000)
Proceeds from sale of strategic and other investments	347,000	4,638,000	114,940,000
Payments for purchase of businesses, net of cash received	(1,892,000)	(36,348,000)	(38,018,000)
Proceeds from sale of subsidiaries	2,550,000	17,068,000	50,557,000
Other, net	(21,643,000)	(9,627,000)	(16,581,000)
Cash used by investing activities	(196,991,000)	(299,653,000)	(419,750,000)
Financing activities
Issuance of notes payable	0	0	296,096,000
Advances on line of credit	305,000,000	50,000,000	130,000,000
Payments on line of credit	(125,000,000)	(50,000,000)	(350,032,000)
Payments on convertible notes	0	(64,472,000)	(60,210,000)
Sale of common stock	36,044,000	29,193,000	19,198,000
Purchase of common stock	(373,584,000)	(35,124,000)	(35,464,000)
Dividends paid	(65,822,000)	(63,245,000)	(57,437,000)
Other, net	5,770,000	(13,502,000)	(3,085,000)
Cash used by financing activities	(217,592,000)	(147,150,000)	(60,934,000)
Net decrease in cash	6,693,000	(31,603,000)	102,113,000
Cash at beginning of year	97,857,000	129,460,000	27,347,000
Cash at end of period	$ 104,550,000	$ 97,857,000	$ 129,460,000