Schedule of Location of Derivatives on Balance Sheet (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Derivatives Fair Value [Line Items]
Derivative assets	$ 35,285	$ 27,151
Derivative liabilities	331,290	244,591
Interest Rate Swaps and Swaptions | Derivative Assets
Derivatives Fair Value [Line Items]
Derivative assets	3,811	11,050
Forward Purchase Commitments - MBS | Derivative Assets
Derivatives Fair Value [Line Items]
Derivative assets	31,145	16,101
Forward Purchase Commitments - MBS | Derivative Liabilities
Derivatives Fair Value [Line Items]
Derivative liabilities		36
Forward Purchase Commitments - Mortgage Loans | Derivative Assets
Derivatives Fair Value [Line Items]
Derivative assets	329
Forward Purchase Commitments - Mortgage Loans | Derivative Liabilities
Derivatives Fair Value [Line Items]
Derivative liabilities		2
Interest Rate Swap | Derivative Liabilities
Derivatives Fair Value [Line Items]
Derivative liabilities	34,774	42,052
Futures Contracts | Derivative Liabilities
Derivatives Fair Value [Line Items]
Derivative liabilities	$ 296,516	$ 202,501