Schedule of Mortgage Backed Securities (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Schedule Of Investment Income Reported Amounts By Category [Line Items]
TBA dollar roll securities - Face	$ 2,850,000	$ 600,000
TBA dollar roll securities - Cost	2,949,433	632,270
TBA dollar roll securities - Fair Market Value	2,962,617	627,187
TBA dollar roll securities - Net Asset (Liability)	$ 13,184	$ (5,083)