Consolidated Statements Of Operations (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Revenues:
Net premiums earned	$ 720,737	$ 683,701
Net investment income	31,506	30,242
Net realized investment (losses) gains	(9,961)us-gaap_RealizedInvestmentGainsLosses	46,712us-gaap_RealizedInvestmentGainsLosses
Other	2,266us-gaap_OtherIncome	2,301us-gaap_OtherIncome
Total revenues	744,548us-gaap_Revenues	762,956us-gaap_Revenues
Expenses:
Losses and loss adjustment expenses	514,400	476,603
Policy acquisition costs	133,847	129,814
Other operating expenses	65,692us-gaap_OtherCostAndExpenseOperating	54,004us-gaap_OtherCostAndExpenseOperating
Interest	750us-gaap_InterestExpense	505us-gaap_InterestExpense
Total expenses	714,689us-gaap_BenefitsLossesAndExpenses	660,926us-gaap_BenefitsLossesAndExpenses
Income before income taxes	29,859	102,030
Income tax expense	3,694us-gaap_IncomeTaxExpenseBenefit	29,381us-gaap_IncomeTaxExpenseBenefit
Net income	$ 26,165us-gaap_NetIncomeLoss	$ 72,649us-gaap_NetIncomeLoss
Net income per share:
Basic (in dollars per share)	$ 0.47us-gaap_EarningsPerShareBasic	$ 1.32us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 0.47us-gaap_EarningsPerShareDiluted	$ 1.32us-gaap_EarningsPerShareDiluted
Weighted average shares outstanding:
Basic (in shares)	55,139	54,977
Diluted (in shares)	55,159	54,986
Dividends paid per share (in dollars per share)	$ 0.6175	$ 0.6150

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