Cash Cash Equivalents and Marketable Securities - Additional Information (Detail) (USD $)	3 Months Ended
	Jun. 30, 2013 Investment	Jun. 30, 2013 Minimum	Dec. 31, 2012 Minimum
Cash, cash equivalents and marketable securities [Line Items]
Marketable securities, minimum original maturity term		90 days	90 days
Long-term marketable securities, minimum original maturity term		1 year	1 year
Marketable securities, average remaining contractual maturity period	7 months 25 days
Number of debt securities in unrealized loss positions	23
Debt securities in unrealized loss positions, total unrealized loss	$ 5,000
Debt securities in unrealized loss positions, total fair market value	$ 7,201,000