Interest Receivable (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Dec. 31, 2012
Interest receivable by investment category
Interest receivable	$ 37,804	$ 44,033
Total MBS
Interest receivable by investment category
Interest receivable	37,783	44,024
Fannie Mae.
Interest receivable by investment category
Interest receivable	14,252	17,597
Freddie Mac.
Interest receivable by investment category
Interest receivable	3,257	2,696
Ginnie Mae.
Interest receivable by investment category
Interest receivable	21	24
Non-Agency MBS
Interest receivable by investment category
Interest receivable	20,253	23,707
Money market and other investments
Interest receivable by investment category
Interest receivable	$ 21	$ 9