Schedule of Concentration of Holdings of Investment Securities by Issuers (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Minimum threshold to identify concentrations of investment securities as a percentage of shareholders' equity	10.00%
Number of separate issuers identified as concentrations	2
Investments issued by IMPAC CMB Trust
Book value	10,295
Market value	11,608
Number of underlying collateral pools	3
Number of securities held	3
Number of collateral pools secured by floating-rate, first lien mortgages originated prior to 2005 on single-family properties in multiple states	3
Investments issued by JP Morgan Chase Commercial Mortgage Securities Corp
Book value	18,077
Market value	18,619
Number of underlying collateral pools	5
Number of securities held	5
Number of collateral pools secured by commercial real estate loans originated prior to 2006	4
Number of collateral pools secured by commercial real estate loans originated during 2010	1