Related Party Transactions - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended					3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011	Mar. 31, 2013 Trust Preferred Securities	Mar. 31, 2013 Maximum	Mar. 31, 2013 Demand Deposits	Dec. 31, 2012 Demand Deposits
Related Party Transaction [Line Items]
Percentage of ownership held by President of Parent Company and Director						1.00%
Cash and cash equivalents	$ 63,854	$ 53,841	$ 100,041	$ 29,720			$ 363	$ 239
Restricted cash	88,397		90,641				283	289
Interest income							0	0
Lease rent paid	90	79
Sublease rent received	44	43
Fees received for managing securitization of marketable securities	$ 670,245		$ 655,509		$ 25,000