Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013 Segment Securities	Dec. 31, 2012 Securities	Dec. 31, 2011 Securities
Significant Of Accounting Policies [Line Items]
Tax benefits related to stock based compensation	$ 0	$ 0	$ 0
Significant uncertain tax positions	0	0
Realized gains or losses on marketable securities	0	0	1,000
Number of securities sold			5
Gross proceeds from sale of securities			13,000,000
Minimum period to liquidate	12 months
Debt securities in an unrealized loss position	33	30
Aggregate fair value of debt securities in an unrealized loss position	31,700,000	13,700,000
Securities in significant unrealized loss position for more than one year	0	0
Concentration of credit risk	The Company has not experienced any credit losses in such accounts and does not believe it is exposed to any significant credit risk on these funds
Off- balance sheet concentrations of credit risk	The Company has no off-balance sheet concentrations of credit risk, such as foreign currency exchange contracts, option contracts or other hedging arrangements
Financial assets or liabilities that were classified as Level 3	0	0
Transfers of asset from Level 1 to Level 2	0	0
Transfers of assets from Level 2 to Level 1	0	0
Transfers of liabilities from Level 1 to Level 2	0	0
Transfers of liabilities from Level 2 to Level 1	0	0
Number of geographic segment in which Company operates	1
Level 3 [Member]
Significant Of Accounting Policies [Line Items]
Financial assets classified as Level 3	0	0
Financial liabilities classified as Level 3	$ 0	$ 0
Maximum [Member]
Significant Of Accounting Policies [Line Items]
Investment maturity period	2 years
Minimum [Member]
Significant Of Accounting Policies [Line Items]
Investment maturity period	1 year