Income Taxes (Schedule of Deferred Tax Assets and Liabilities) (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Deferred tax asset:
Loss reserve discounting	$ 100,806,000	$ 77,216,000
Unearned premiums	176,465,000	165,075,000
Other-than-temporary impairments	26,509,000	45,367,000
Restricted stock units	62,442,000	60,061,000
Other	89,761,000	101,131,000
Gross deferred tax asset	455,983,000	448,850,000
Less valuation allowance	(4,037,000)	(1,335,000)
Deferred tax asset	451,946,000	447,515,000
Deferred tax liability:
Amortization of intangibles	20,316,000	22,747,000
Deferred policy acquisition costs	162,344,000	152,001,000
Unrealized investment gains	115,499,000	175,111,000
Other	160,598,000	135,108,000
Deferred tax liability	458,757,000	484,967,000
Net deferred tax asset (liability)	(6,811,000)	(37,452,000)
Current Federal income taxes	55,763,000	67,623,000
Operating Loss Carryforwards [Line Items]
Taxes Payable, Current		67,623,000
Tax Credit Carryforward, Valuation Allowance	4,000,000	$ 1,300,000
Foreign Tax Authority (expiration 2031) [Member]
Operating Loss Carryforwards [Line Items]
Operating loss carryforwards	$ 6,100,000