Marketable Investments - Summary of Company's Marketable Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		$ 80,988
Gross Unrealized Gains		117
Gross Unrealized Losses		(92)
Total		81,013us-gaap_AvailableForSaleSecurities
State and Municipal Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		6,809
Gross Unrealized Gains		5
Gross Unrealized Losses
Total		6,814
Federal Agency and Corporate Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	55,005	74,179
Gross Unrealized Gains	13	112
Gross Unrealized Losses	(133)	(92)
Total	$ 54,885	$ 74,199

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

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

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