Income Taxes (Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Deferred tax assets:
20% of net unearned premiums	$ 61,067	$ 58,448
Discounting of loss reserves and salvage and subrogation recoverable for tax purposes	15,090	12,769
Write-down of impaired investments	293	314
Expense accruals	14,432	8,099
Other deferred tax assets	6,401	3,348
Total gross deferred tax assets	97,283	82,978
Deferred tax liabilities:
Deferred policy acquisition costs	(51,869)	(48,964)
Tax liability on net unrealized gain on securities carried at fair value	(56,531)	(41,273)
Tax depreciation in excess of book depreciation	(12,632)	(8,105)
Undistributed earnings of insurance subsidiaries	(3,382)	(2,855)
Tax amortization in excess of book amortization	(4,666)	(3,264)
Other deferred tax liabilities	(9,335)	(6,481)
Total gross deferred tax liabilities	(138,415)	(110,942)
Net deferred tax liabilities	$ (41,132)	$ (27,964)