Interim Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Net Income	$ 13,242us-gaap_NetIncomeLoss	$ 13,229us-gaap_NetIncomeLoss
Other Comprehensive Income:
Unrealized gains on investments in marketable securities	3,987	9,598
Reclassification adjustment for realized gains on sale of securities	(341)	(136)
Income tax expense related to items of other comprehensive income	(1,366)	(3,650)
Other comprehensive income, net of tax	2,280	5,812
Comprehensive Income	$ 15,522us-gaap_ComprehensiveIncomeNetOfTax	$ 19,041us-gaap_ComprehensiveIncomeNetOfTax

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Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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Amount after tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income for unrealized gain (loss) realized upon the sale of available-for-sale securities.

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Amount before tax and reclassification adjustments of unrealized holding gain (loss) on available-for-sale securities.

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