CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Unaudited) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Statement of Comprehensive Income [Abstract]
Net income	$ 6,343us-gaap_NetIncomeLoss	$ 12,363us-gaap_NetIncomeLoss
Other comprehensive income, net of tax:
Foreign currency translation adjustments, net of $0 tax in the three months ended March 31, 2015 and 2014 (Note 2)	35	(6)
Unrealized gain on marketable securities, net of $0 tax in the three months ended March 31, 2015 and 2014 (Note 2)	56	147
Amortization of defined benefit pension items, net of tax of $4 and $4 in the three months ended March 31, 2015 and 2014, respectively (Note 2)	14	14
Total other comprehensive income	105	155
Total comprehensive income	$ 6,448us-gaap_ComprehensiveIncomeNetOfTax	$ 12,518us-gaap_ComprehensiveIncomeNetOfTax

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

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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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Amount after tax and reclassification adjustments, of (increase) decrease in accumulated other comprehensive (income) loss related to pension and other postretirement defined benefit plans.

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

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