Supplementary Balance Sheet Information - Aggregate Fair Value and Unrealized Holding Gains and Losses by Major Security Type (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available- for- sale securities, Amortized cost	$ 5,942
Available- for- sale securities, Aggregate fair value	5,890us-gaap_AvailableForSaleSecurities
Available- for- sale securities, Unrealized Gains	2
Available- for- sale securities, Unrealized losses	(54)
Held- to- maturity securities, Amortized cost		18,371us-gaap_HeldToMaturitySecurities
Held- to- maturity securities, Aggregate fair value		18,228
Held- to- maturity securities, Unrealized Gains		51
Held- to- maturity securities, Unrealized losses		(194)
Long Term Marketable Securities [Member] \| Government and Corporate Bonds [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Available- for- sale securities, Amortized cost	5,942
Available- for- sale securities, Aggregate fair value	5,890
Available- for- sale securities, Unrealized Gains	2
Available- for- sale securities, Unrealized losses	(54)
Held- to- maturity securities, Amortized cost		13,106
Held- to- maturity securities, Aggregate fair value		12,949
Held- to- maturity securities, Unrealized Gains		24
Held- to- maturity securities, Unrealized losses		(181)
Short Term Marketable Securities [Member] \| Government and Corporate Bonds [Member]
Schedule Of Available For Sale Securities And Held To Maturity Securities [Line Items]
Held- to- maturity securities, Amortized cost		5,265
Held- to- maturity securities, Aggregate fair value		5,279
Held- to- maturity securities, Unrealized Gains		27
Held- to- maturity securities, Unrealized losses		$ (13)

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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in equity securities classified as available-for-sale.

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Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized gain on investments in debt securities classified as held-to-maturity.

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Amount of accumulated unrealized loss on investments in debt securities classified as held-to-maturity.

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Fair value of investments in debt securities classified as held-to-maturity.

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