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Financial Instruments - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Financial Instruments [Line Items]
Realized Gain (Loss) on Marketable Securities, Cost Method Investments, and Other Investments	$ 458,000	$ 771,000	$ 74,000
Maximum [Member] | Corporate Bond Securities [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	30 years
Maximum [Member] | Municipal Bonds [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	5 years
Maximum [Member] | US Treasury and Government Short-term Debt Securities [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	7 years
Minimum [Member] | Corporate Bond Securities [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	1 year
Minimum [Member] | Municipal Bonds [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	1 year
Minimum [Member] | US Treasury and Government Short-term Debt Securities [Member]
Financial Instruments [Line Items]
Available for Sale Securities Maturity Period	1 year

X

- Definition

Number of maturity year relating to investment securities.

+ References

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- Definition

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.

+ References

No definition available.

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