Common Stock - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Jul. 23, 2012	Feb. 29, 2012
IPO [Member]
Class of Stock [Line Items]
Common stock sold		10,906,941
Sale of Stock, Price Per Share		$ 12
Proceeds from Issuance of Common Stock		$ 125.1
Sale of Stock, Consideration Received on Transaction		112.8
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions		8.8
Payments of Stock Issuance Costs		$ 3.5
Secondary Offering [Member]
Class of Stock [Line Items]
Common stock sold	9,775,000
Sale of Stock, Price Per Share	$ 15.40
Proceeds from Issuance of Common Stock	$ 55.8
Sale of Stock, Consideration Received on Transaction	51.9
Investment Banking, Advisory, Brokerage, and Underwriting Fees and Commissions	2.7
Payments of Stock Issuance Costs	$ 1.2
Shares Offered By Company [Member] | IPO [Member]
Class of Stock [Line Items]
Common stock sold		10,422,645
Shares Offered By Company [Member] | Secondary Offering [Member]
Class of Stock [Line Items]
Common stock sold	3,625,000
Shares Offered By Selling Stockholders [Member] | IPO [Member]
Class of Stock [Line Items]
Common stock sold		484,296
Shares Offered By Selling Stockholders [Member] | Secondary Offering [Member]
Class of Stock [Line Items]
Common stock sold	6,150,000