Cash, Cash Equivalents, and Short-Term Investments - Summary of Cost and Estimated Fair Value of Short-Term Investments (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Short Term Investments [Abstract]
Amortized Cost of short-term investments, Due within one year	$ 24,442
Amortized Cost of short-term investments, Due within two years	10,714
Short-term investments, Amortized Cost	35,156	38,373
Estimated fair value of short-term investments, Due within one year	24,459
Estimated fair value of short-term investments, Due within two years	10,708
Short-term investments, Estimated Fair Value	$ 35,167	$ 38,381	[1]

[1] The Condensed Consolidated Balance Sheet as of December 31, 2013 has been derived from the audited consolidated financial statements at that date but does not include all of the information and footnotes required by generally accepted accounting principles for complete financial statements.