Net Income (Loss) Per Share Attributable to Common Stockholders - Calculation of Basic and Diluted Net Income (Loss) Per Share Attributable to Common Stockholders (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012	Jun. 30, 2011	Jun. 30, 2010
Numerator:
Net income (loss)	$ (6,684)	$ 4,803	$ (37,348)	$ 9,830	$ (29,705)
Accretion of redeemable convertible preferred stock	(312)	(320)	(308)	(633)	(640)
Net income attributable to participating securities	0	(3,721)	0	(7,558)	0
Net income (loss) attributable to common stockholders - basic	(6,996)	762	(37,656)	1,639	(30,345)
Undistributed earnings reallocated to participating securities	0	349	0	671	0
Net income (loss) attributable to common stockholders - diluted	$ (6,996)	$ 1,111	$ (37,656)	$ 2,310	$ (30,345)
Denominator:
Weighted-average shares outstanding - Basic, shares	21,104,219	17,156,445	73,908,631	18,163,977	23,157,576
Effect of potentially dilutive securities:
Common stock options, shares	0	10,465,912	0	9,931,509	0
Weighted-average shares outstanding - Diluted, shares	21,104,219	27,622,357	73,908,631	28,095,486	23,157,576
Net income (loss) per share attributable to common stockholders:
Earnings Per Share, Basic (usd per share)	$ (0.33)	$ 0.04	$ (0.51)	$ 0.09	$ (1.31)
Earnings Per Share, Diluted (usd per share)	$ (0.33)	$ 0.04	$ (0.51)	$ 0.08	$ (1.31)