Stockholders' Equity - Additional Information (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	9 Months Ended			0 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012 Maximum	Oct. 10, 2012 Subsequent Event [Member]
Shareholders Equity [Line Items]
Dividend declared date				Oct. 10, 2012
Dividend declared per share				$ 0.21
Dividends payment date				Nov. 26, 2012
Dividends payable record date				Oct. 29, 2012
Options vesting and exercisable			8 years
Options termination period after the end of the relevant vesting period (in months)	13 months
Total stock-based compensation expense	$ 3,450	$ 2,925
Total unrecognized compensation expense	$ 21,447
Weighted average period over which total unrecognized compensation expense will be recognized (in years)	4 years 10 months 17 days