Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 88,966	$ 76,361
Unrealized Gains	171	128
Unrealized Losses	(35)	(28)
Fair Value	89,102	76,461
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	34,398	41,545
Unrealized Gains	117	75
Unrealized Losses	(5)	(20)
Fair Value	34,510	41,600
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	51,625	31,868
Unrealized Gains	51	52
Unrealized Losses	(29)	(4)
Fair Value	51,647	31,916
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,943	2,948
Unrealized Gains	3	1
Unrealized Losses	(1)	(4)
Fair Value	$ 2,945	$ 2,945