Related Party Transactions (Details) (Class A Common Stock, USD $)	3 Months Ended
	Jun. 30, 2013
Affiliates of Ares Management LLC, Leonard Green & Partners, L.P. and WL Ross & Co. LLC
Related party transactions
Share price of common stock offered in a secondary public offering previously held by affiliates	$ 26.75
Affiliates of Ares Management LLC, Leonard Green & Partners, L.P. and WL Ross & Co. LLC | Maximum
Related party transactions
Number of shares issued in a secondary public offering previously held by affiliates	8,000,000
Commonwealth Bank of Australia | Servicing Agreement | Minimum
Related party transactions
Beneficial ownership interest owned (as a percent)	5.00%