Financial Instruments - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended
Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Financial Instruments [Line Items]
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments	$ (17,000)	$ 716,000	$ 117,000	$ 949,000

This item represents the total realized gain (loss) included in earnings for the period as a result of selling marketable securities categorized as trading, available-for-sale, or held-to-maturity and any gains or losses realized during the period from the sale of investments accounted for under the cost method of accounting and/or investments that are separately or otherwise not categorized as trading, available-for-sale, or held-to-maturity. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration