Annual report pursuant to Section 13 and 15(d)

Schedule of Available-for-sale Securities Reconciliation (Details)

v3.8.0.1
Schedule of Available-for-sale Securities Reconciliation (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Dec. 31, 2016
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face $ 29,396,680 $ 16,290,758
Unamortized Premium 1,370,959 826,062
Accretable Purchase Discount (700,671) (674,303)
Credit Reserve Purchase Discount (653,613) (367,437)
Amortized Cost 20,856,658 12,927,650
Unrealized Gain 544,198 432,398
Unrealized Loss (180,037) (243,877)
Available-for-sale securities, at fair value 21,220,819 13,116,171
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 20,023,621 13,571,417
Unamortized Premium 1,302,535 818,122
Accretable Purchase Discount (24,638) (42,923)
Credit Reserve Purchase Discount 0 0
Amortized Cost 18,359,746 11,384,721
Unrealized Gain 53,104 79,040
Unrealized Loss (174,125) (237,287)
Available-for-sale securities, at fair value 18,238,725 11,226,474
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Fixed Income Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 17,081,849 10,609,522
Unamortized Premium 1,079,246 571,749
Accretable Purchase Discount (24,638) (42,923)
Credit Reserve Purchase Discount 0 0
Amortized Cost 18,136,457 11,138,348
Unrealized Gain 42,149 66,968
Unrealized Loss (134,969) (208,190)
Available-for-sale securities, at fair value 18,043,637 10,997,126
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | Interest-Only-Strip [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 2,941,772 2,961,895
Unamortized Premium 223,289 246,373
Accretable Purchase Discount 0 0
Credit Reserve Purchase Discount 0 0
Amortized Cost 223,289 246,373
Unrealized Gain 10,955 12,072
Unrealized Loss (39,156) (29,097)
Available-for-sale securities, at fair value 195,088 229,348
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 9,373,059 2,719,341
Unamortized Premium 68,424 7,940
Accretable Purchase Discount (676,033) (631,380)
Credit Reserve Purchase Discount (653,613) (367,437)
Amortized Cost 2,496,912 1,542,929
Unrealized Gain 491,094 353,358
Unrealized Loss (5,912) (6,590)
Available-for-sale securities, at fair value 2,982,094 1,889,697
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fixed Income Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 3,758,134 2,533,806
Unamortized Premium 2,757 3,577
Accretable Purchase Discount (676,033) (631,380)
Credit Reserve Purchase Discount (653,613) (367,437)
Amortized Cost 2,431,245 1,538,566
Unrealized Gain 488,931 353,240
Unrealized Loss (3,166) (6,386)
Available-for-sale securities, at fair value 2,917,010 1,885,420
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Interest-Only-Strip [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 5,614,925 185,535
Unamortized Premium 65,667 4,363
Accretable Purchase Discount 0 0
Credit Reserve Purchase Discount 0 0
Amortized Cost 65,667 4,363
Unrealized Gain 2,163 118
Unrealized Loss (2,746) (204)
Available-for-sale securities, at fair value $ 65,084 $ 4,277