Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 32,024	$ 44,294	$ 65,110	$ 114,771
Other comprehensive income, net of tax:
Unrealized gain on available-for-sale securities, before tax	30	9,546	3,692	8,583
Income tax expense related to unrealized gain on available-for-sale securities	(13)	(3,591)	(1,688)	(3,228)
Other comprehensive income, net of tax	17	5,955	2,004	5,355
Comprehensive income	$ 32,041	$ 50,249	$ 67,114	$ 120,126

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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Gross appreciation or the gross loss in value of the total of unsold available-for-sale securities (except when designated as a fair value hedge or which had been determined to have had an other than temporary decline in fair value below its amortized cost basis). While for technical reasons this element has no balance attribute, the default assumption is a credit balance consistent with its label.

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Tax effect of the gross appreciation or the gross loss, net of reclassification adjustment, in the value of the total unsold available-for-sale securities at the end of an accounting period.

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