Income Taxes (Deferred Tax Assets And Liabilities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Deferred tax assets:
20% of net unearned premium	$ 66,353	$ 61,039
Capital loss carryforward	0	7,108
Discounting of loss reserves and salvage and subrogation recoverable for tax purposes	15,019	15,034
Write-down of impaired investments	1,723	4,638
Tax credit carryforward	37,557	20,060
Expense accruals	10,910	11,632
Other deferred tax assets	4,860	3,568
Total gross deferred tax assets	136,422	123,079
Deferred tax liabilities:
Deferred acquisition costs	(65,069)	(60,000)
Tax liability on net unrealized gain on securities carried at fair value	(48,483)	(31,997)
Tax depreciation in excess of book depreciation	(10,191)	(15,164)
Undistributed earnings of insurance subsidiaries	(4,499)	(3,962)
Tax amortization in excess of book amortization	(914)	(442)
Other deferred tax liabilities	(7,711)	(5,003)
Total gross deferred tax liabilities	(136,867)	(116,568)
Net deferred tax (liabilities) assets	$ (445)	$ 6,511