Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net Income	$ 53,369us-gaap_NetIncomeLoss	$ 64,613us-gaap_NetIncomeLoss	$ 59,300us-gaap_NetIncomeLoss
Other Comprehensive Income (Loss):
Unrealized gains (losses) on investments in marketable securities	30,416	(7,211)	24,739
Reclassification adjustment for realized gains on sale of securities	(379)	(39)	(1,640)
Income tax (expense) benefit related to items of other comprehensive income (loss)	(11,614)	2,627	(8,993)
Other comprehensive income (loss), net of tax	18,423	(4,623)	14,106
Comprehensive Income	$ 71,792us-gaap_ComprehensiveIncomeNetOfTax	$ 59,990us-gaap_ComprehensiveIncomeNetOfTax	$ 73,406us-gaap_ComprehensiveIncomeNetOfTax

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