Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 76,502	$ 76,361
Unrealized Gains	162	128
Unrealized Losses	(30)	(28)
Fair Value	76,634	76,461
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	36,586	41,545
Unrealized Gains	117	75
Unrealized Losses		(20)
Fair Value	36,703	41,600
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	37,219	31,868
Unrealized Gains	43	52
Unrealized Losses	(29)	(4)
Fair Value	37,233	31,916
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,697	2,948
Unrealized Gains	2	1
Unrealized Losses	(1)	(4)
Fair Value	$ 2,698	$ 2,945