Marketable Securities Classified as Available-for-Sale (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 112,458	$ 117,861
Gross Unrealized Gain	131	372
Gross Unrealized Loss	(45)	(46)
Fair Value	112,544	118,187
Corporate bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	45,414	49,545
Gross Unrealized Gain	75	203
Gross Unrealized Loss	(7)	(4)
Fair Value	45,482	49,744
Asset-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	21,222	23,079
Gross Unrealized Gain	12	70
Gross Unrealized Loss	(8)
Fair Value	21,226	23,149
Mortgage-backed securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	15,110	12,064
Gross Unrealized Gain	33	40
Gross Unrealized Loss	(26)	(15)
Fair Value	15,117	12,089
Commercial paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,890	1,200
Gross Unrealized Gain	2
Gross Unrealized Loss
Fair Value	13,892	1,200
Government and agency securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,255	23,431
Gross Unrealized Gain	9	43
Gross Unrealized Loss		(27)
Fair Value	12,264	23,447
Municipal bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,817	6,273
Gross Unrealized Gain		13
Gross Unrealized Loss	(4)
Fair Value	3,813	6,286
Certificates of deposit [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	750	1,003
Gross Unrealized Gain		1
Gross Unrealized Loss
Fair Value	750	1,004
Floating rate notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		1,266
Gross Unrealized Gain		2
Fair Value		$ 1,268