Federal Income Taxes (Deferred Tax Assets and Liabilities) (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Income Tax Disclosure [Abstract]
Net loss reserve discounting	$ 97,561,000	$ 99,768,000
Net unearned premiums	58,981,000	53,191,000
Employee benefits	39,752,000	33,100,000
Long-term incentive compensation plans	10,078,000	8,471,000
Temporary investment write-downs	8,236,000	13,251,000
Net operating loss	12,120,000	4,183,000
Tax credits	14,150,000	10,938,000
Other	9,056,000	7,638,000
Total deferred tax assets	249,934,000	230,540,000
Deferred policy acquisition costs	53,187,000	46,729,000
Unrealized gains on investment securities	67,501,000	53,996,000
Other investments-related items, net	2,488,000	4,034,000
Accelerated depreciation and amortization	7,622,000	6,295,000
Total deferred tax liabilities	130,798,000	111,054,000
Net deferred federal income tax asset	119,136,000	119,486,000
Tax benefits related to compensation expense deductions for share-based compensation awards	$ 17,700,000	$ 16,600,000	$ 16,700,000

The tax effect as of the balance sheet date of the amount of the estimated future tax deductions, before any related valuation allowance, arising from unrealized losses on securities which can only be deducted for tax purposes when the losses are realized, and which can only be realized if sufficient tax-basis income is generated in future periods to enable the deduction to be taken.

No definition available.