Subsequent Event (Details) (Shares issued, USD $)	1 Months Ended
	May 15, 2012	Apr. 30, 2012
Shares issued
Information related to subsequent events
Agreement to issue stock, number of shares		10,000,000
Agreement to issue stock, price per share (in dollars per share)		$ 21.2887
Total investment by related party upon issuance of company's common stock in common stock purchase agreement		$ 212,887,000
Maximum percentage decline against S & P benchmark value, before common stock purchase agreement termination option activated for related party	30.00%