Investments (Schedule of Available-for-sale Securities Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 506,866	$ 504,564
Gross Unrealized Gains	9,150	8,738
Gross Unrealized Losses	(1,550)	(1,419)
Estimated Fair Value	514,466us-gaap_AvailableForSaleSecurities	511,883us-gaap_AvailableForSaleSecurities
U.S. Government agencies [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	24,805	26,959
Gross Unrealized Gains	411	334
Gross Unrealized Losses	(14)	(23)
Estimated Fair Value	25,202	27,270
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	385,369	378,339
Gross Unrealized Gains	4,298	4,299
Gross Unrealized Losses	(1,391)	(1,196)
Estimated Fair Value	388,276	381,442
State and political subdivisions [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	95,483	98,056
Gross Unrealized Gains	3,379	3,093
Gross Unrealized Losses	(145)	(200)
Estimated Fair Value	98,717	100,949
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,209	1,210
Gross Unrealized Gains	1,062	1,012
Gross Unrealized Losses
Estimated Fair Value	$ 2,271	$ 2,222

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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