Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 96,735	$ 76,361
Unrealized Gains	59	128
Unrealized Losses	(163)	(28)
Fair Value	96,631us-gaap_AvailableForSaleSecurities	76,461us-gaap_AvailableForSaleSecurities
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,820	41,545
Unrealized Gains	52	75
Unrealized Losses	(17)	(20)
Fair Value	27,855	41,600
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	65,487	31,868
Unrealized Gains	5	52
Unrealized Losses	(144)	(4)
Fair Value	65,348	31,916
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,428	2,948
Unrealized Gains	2	1
Unrealized Losses	(2)	(4)
Fair Value	$ 3,428	$ 2,945

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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