Condensed Consolidated Statements of Comprehensive Income (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Net income	$ 5,963us-gaap_NetIncomeLoss	$ 9,018us-gaap_NetIncomeLoss
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	249	(596)
Total other comprehensive income (loss), net of tax	285	(608)
Comprehensive income	6,248us-gaap_ComprehensiveIncomeNetOfTax	8,410us-gaap_ComprehensiveIncomeNetOfTax
Auction Rate Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	5	(17)
Available-for-sale Securities [Member]
Other comprehensive income (loss), net of tax:
Change in unrealized losses on securities, net of tax	$ 31	$ 5

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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 and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature.

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Amount after tax and reclassification adjustments of other comprehensive income (loss).

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