Computation of Basic and Diluted Net Income Per Share Attributable to Common Stockholders (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Numerator (basic and diluted):
Net income	$ 4,636	$ 2,010
Less: accretion of redemption premium expense		(1,523)
Net income attributable to common stockholders for basic EPS	4,636	487
Add back: accretion of redemption premium related to dilutive redeemable preferred stock		(174)
Net income attributable to common stockholders for diluted EPS	$ 4,636	$ 313
Denominator (basic):
Weighted average common shares outstanding	32,226	1,546
Denominator (diluted):
Weighted average common shares outstanding	32,226	1,546
Dilutive stock options	1,615	916
Weighted average common shares from stock warrants		2,425
Weighted average common shares from preferred stock		12,099
Net weighted average common shares outstanding	33,841	16,986
Net income per share attributable to holders of common stock:
Basic	$ 0.14	$ 0.32
Diluted	$ 0.14	$ 0.02