Schedule of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 92,017	$ 76,361
Unrealized Gains	96	128
Unrealized Losses	(87)	(28)
Fair Value	92,026	76,461
Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	35,595	41,545
Unrealized Gains	68	75
Unrealized Losses	(4)	(20)
Fair Value	35,659	41,600
Corporate bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	53,483	31,868
Unrealized Gains	25	52
Unrealized Losses	(83)	(4)
Fair Value	53,425	31,916
Certificates of Deposit
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,939	2,948
Unrealized Gains	3	1
Unrealized Losses		(4)
Fair Value	$ 2,942	$ 2,945