Quarterly report pursuant to Section 13 or 15(d)

Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details)

v3.2.0.727
Derivative Instruments and Hedging Activities Interest Rate Sensitive Assets/Liabilities (Details) - USD ($)
$ in Thousands
Jun. 30, 2015
Dec. 31, 2014
Derivatives, Fair Value [Line Items]    
Available-for-sale securities, at fair value $ 12,807,658 $ 14,341,102
Interest-Only-Strip [Member]    
Derivatives, Fair Value [Line Items]    
Available-for-sale securities, at fair value $ 49,278 $ 55,686