Cash, Cash Equivalents and Short-Term Investments and Long-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 81,380	$ 92,094
Unrealized Holdings Gains	39	86
Unrealized Holdings Losses	5	11
Fair Value	81,414	92,169
Cash
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,819	5,939
Fair Value	5,819	5,939
Money market funds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,302	18,322
Fair Value	14,302	18,322
Cash and Cash Equivalents
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,121	24,261
Fair Value	20,121	24,261
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	48,953	40,558
Unrealized Holdings Gains	25	37
Unrealized Holdings Losses	3	4
Fair Value	48,975	40,591
Short-term Investments | Commercial Paper
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,998	2,495
Unrealized Holdings Gains	1
Fair Value	1,999	2,495
Short-term Investments | Corporate bonds and medium-term notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	27,181	19,539
Unrealized Holdings Gains	13	13
Unrealized Holdings Losses	3	4
Fair Value	27,191	19,548
Short-term Investments | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	6,108	1,203
Unrealized Holdings Gains	4	1
Fair Value	6,112	1,204
Short-term Investments | US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,506	16,976
Unrealized Holdings Gains	7	23
Fair Value	13,513	16,999
Short-term Investments | Variable rate demand notes ("VRDNs")
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	160	345
Fair Value	160	345
Other Long-term Investments
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,306	27,275
Unrealized Holdings Gains	14	49
Unrealized Holdings Losses	2	7
Fair Value	12,318	27,317
Other Long-term Investments | Corporate bonds and medium-term notes
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,811	16,776
Unrealized Holdings Gains	12	33
Unrealized Holdings Losses		7
Fair Value	8,823	16,802
Other Long-term Investments | Municipal bonds
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,495	1,000
Unrealized Holdings Gains	2	2
Unrealized Holdings Losses	2
Fair Value	3,495	1,002
Other Long-term Investments | US Government Agencies Debt Securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost		9,499
Unrealized Holdings Gains		14
Fair Value		$ 9,513