Income Taxes (Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets:
20% of net unearned premiums	$ 77,104	$ 75,406
Discounting of loss reserves and salvage and subrogation recoverable for tax purposes	9,864	9,518
Write-down of impaired investments	726	857
Tax credit carryforward	47,238	36,349
Expense accruals	11,090	11,264
Other deferred tax assets	8,828	9,596
Total gross deferred tax assets	154,850	142,990
Deferred tax liabilities:
Deferred policy acquisition costs	(70,289)	(70,617)
Tax liability on net unrealized gain on securities carried at fair value	(15,612)	(23,095)
Tax depreciation in excess of book depreciation	(10,446)	(10,742)
Undistributed earnings of insurance subsidiaries	(3,985)	(4,022)
Tax amortization in excess of book amortization	(3,030)	(2,514)
Other deferred tax liabilities	(6,211)	(8,769)
Total gross deferred tax liabilities	(109,573)	(119,759)
Net deferred tax assets	$ 45,277	$ 23,231