Investments in Marketable Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Investment [Line Items]
Unrealized gains on marketable securities	$ 173,000	$ 196,000
Unrealized losses on marketable securities	$ 13,000
Maturity date of investments in marketable securities, range start	2014-04
Maturity date of investments in marketable securities, range end	2016-12
Weighted average maturity date	2015-03