Quarterly report pursuant to Section 13 or 15(d)

Schedule of Notional Amounts of Derivative Positions (Details)

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Schedule of Notional Amounts of Derivative Positions (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended 6 Months Ended
Jun. 30, 2014
Jun. 30, 2013
Jun. 30, 2014
Jun. 30, 2013
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance $ 43,576,146 $ 27,041,328 $ 37,366,610 $ 22,377,656
Derivative, Notional Amount, Additions 14,770,625 20,979,761 30,605,735 38,413,446
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (14,967,554) (3,758,484) (24,593,128) (16,528,497)
Derivative, Notional Amount, Ending Balance 43,379,217 44,262,605 43,379,217 44,262,605
Derivative, Average Notional Amount 43,273,172 32,776,778 42,023,975 28,266,287
Gain (Loss) on Sale of Derivatives (38,149) 25,765 (37,191) (45,168)
Inverse Interest-Only Securities [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 1,412,374 1,960,087 1,525,845 1,909,351
Derivative, Notional Amount, Additions 0 15,576 0 230,261
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (88,724) (176,691) (202,195) (340,640)
Derivative, Notional Amount, Ending Balance 1,323,650 1,798,972 1,323,650 1,798,972
Derivative, Average Notional Amount 1,372,535 1,895,789 1,421,330 1,908,919
Gain (Loss) on Sale of Derivatives 0 0 193 0
Interest Rate Swap [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 21,663,148 16,685,000 19,619,000 14,070,000
Derivative, Notional Amount, Additions 8,465,000 1,800,000 11,409,148 12,575,000
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (6,500,000) 0 (7,400,000) (8,160,000)
Derivative, Notional Amount, Ending Balance 23,628,148 18,485,000 23,628,148 18,485,000
Derivative, Average Notional Amount 23,467,489 17,655,220 21,324,091 16,267,624
Gain (Loss) on Sale of Derivatives (2,983) 0 (3,005) (58,692)
Credit Default Swap [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 125,000 437,496 427,073 438,440
Derivative, Notional Amount, Additions 0 1,300,000 0 1,300,000
Derivative, Notional Amount, Settlement Termination Expiration or Exercise 0 (107,092) (302,073) (108,036)
Derivative, Notional Amount, Ending Balance 125,000 1,630,404 125,000 1,630,404
Derivative, Average Notional Amount 125,000 764,914 152,059 602,283
Gain (Loss) on Sale of Derivatives 0 (12,352) (13,705) (12,352)
Interest Rate Swaption [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 9,500,000 5,800,000 5,130,000 4,950,000
Derivative, Notional Amount, Additions 3,250,000 750,000 7,150,000 1,600,000
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (1,300,000) (300,000) (830,000) (300,000)
Derivative, Notional Amount, Ending Balance 11,450,000 6,250,000 11,450,000 6,250,000
Derivative, Average Notional Amount 10,412,088 5,748,352 9,699,558 5,646,133
Gain (Loss) on Sale of Derivatives (2,178) (3,983) (3,396) (3,983)
Forward Contracts [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance (1,022,000) 2,150,000 603,000 953,000
Derivative, Notional Amount, Additions (2,032,000) (1,494,000) (2,924,000) 4,100,000
Derivative, Notional Amount, Settlement Termination Expiration or Exercise 2,682,000 (3,377,000) 1,949,000 (7,774,000)
Derivative, Notional Amount, Ending Balance (372,000) (2,721,000) (372,000) (2,721,000)
Derivative, Average Notional Amount 660,308 724,725 593,746 805,403
Gain (Loss) on Sale of Derivatives (26,530) 32,767 (14,677) 20,114
Options Held [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 1,500,000 0 0 0
Derivative, Notional Amount, Additions 0 (502,000) 1,500,000 (502,000)
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (1,500,000) 292,000 (1,500,000) 292,000
Derivative, Notional Amount, Ending Balance 0 (210,000) 0 (210,000)
Derivative, Average Notional Amount 901,099 130,901 580,110 65,812
Gain (Loss) on Sale of Derivatives (5,332) 29,197 (5,332) 29,197
Swap [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 10,000,000 0 10,000,000 0
Derivative, Notional Amount, Additions 4,000,000 19,000,000 12,000,000 19,000,000
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (8,000,000) 0 (16,000,000) 0
Derivative, Notional Amount, Ending Balance 6,000,000 19,000,000 6,000,000 19,000,000
Derivative, Average Notional Amount 5,571,429 5,532,967 7,773,481 2,781,768
Gain (Loss) on Sale of Derivatives (1,460) 0 2,427 0
Total Return Swap [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 243,987   49,629  
Derivative, Notional Amount, Additions 339,869   536,881  
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (7,378)   (10,032)  
Derivative, Notional Amount, Ending Balance 576,478   576,478  
Derivative, Average Notional Amount 393,910   274,573  
Gain (Loss) on Sale of Derivatives 0   0  
Short US Treasury Securities [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 0 0 0 0
Derivative, Notional Amount, Additions (125,000) (400,000) (125,000) (400,000)
Derivative, Notional Amount, Settlement Termination Expiration or Exercise 125,000 400,000 125,000 400,000
Derivative, Notional Amount, Ending Balance 0 0 0 0
Derivative, Average Notional Amount 1,374 26,703 691 13,425
Gain (Loss) on Sale of Derivatives 2 (876) 2 (876)
Forward Purchase Commitment [Member]
        
Derivative [Line Items]        
Derivative, Notional Amount, Beginning Balance 153,637 8,745 12,063 56,865
Derivative, Notional Amount, Additions 872,756 510,185 1,058,706 510,185
Derivative, Notional Amount, Settlement Termination Expiration or Exercise (378,452) (489,701) (422,828) (537,821)
Derivative, Notional Amount, Ending Balance 647,941 29,229 647,941 29,229
Derivative, Average Notional Amount 367,940 297,207 204,336 174,920
Gain (Loss) on Sale of Derivatives $ 332 $ (18,988) $ 302 $ (18,576)