Company and Basis of Presentation - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2011	Jun. 02, 2011 IPO	Jun. 02, 2011 Redeemable convertible preferred stock	Jun. 02, 2011 Series B preferred stock
Nature Of Company [Line Items]
Issuance of common stock at public offering	12,021,250
Common stock issuance price		$ 18.00
Proceeds from issuance of common stock	$ 201,236,000
Underwriting discounts and commissions	15,100,000
Initial public offering costs	$ 4,295,000
Redeemable convertible preferred stock converted to shares of common stock			34,534,125	303,855