Quarterly report pursuant to Section 13 or 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
Mar. 31, 2018
Dec. 31, 2017
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face $ 29,684,919 $ 29,396,680
Unamortized Premium 1,359,967 1,370,959
Accretable Purchase Discount (681,749) (700,671)
Credit Reserve Purchase Discount (712,017) (653,613)
Amortized Cost 21,040,250 20,856,658
Unrealized Gain 538,549 544,198
Unrealized Loss (519,422) (180,037)
Available-for-sale securities, at fair value 21,059,377 21,220,819
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 20,381,425 20,023,621
Unamortized Premium 1,283,567 1,302,535
Accretable Purchase Discount (24,501) (24,638)
Credit Reserve Purchase Discount 0 0
Amortized Cost 18,525,396 18,359,746
Unrealized Gain 29,177 53,104
Unrealized Loss (512,409) (174,125)
Available-for-sale securities, at fair value 18,042,164 18,238,725
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 17,266,330 17,081,849
Unamortized Premium 1,059,269 1,079,246
Accretable Purchase Discount (24,501) (24,638)
Credit Reserve Purchase Discount 0 0
Amortized Cost 18,301,098 18,136,457
Unrealized Gain 14,803 42,149
Unrealized Loss (468,055) (134,969)
Available-for-sale securities, at fair value 17,847,846 18,043,637
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 3,115,095 2,941,772
Unamortized Premium 224,298 223,289
Accretable Purchase Discount 0 0
Credit Reserve Purchase Discount 0 0
Amortized Cost 224,298 223,289
Unrealized Gain 14,374 10,955
Unrealized Loss (44,354) (39,156)
Available-for-sale securities, at fair value 194,318 195,088
Mortgage-backed Securities, Issued by Private Enterprises [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 9,303,494 9,373,059
Unamortized Premium 76,400 68,424
Accretable Purchase Discount (657,248) (676,033)
Credit Reserve Purchase Discount (712,017) (653,613)
Amortized Cost 2,514,854 2,496,912
Unrealized Gain 509,372 491,094
Unrealized Loss (7,013) (5,912)
Available-for-sale securities, at fair value 3,017,213 2,982,094
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Fixed Income Securities [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 3,807,719 3,758,134
Unamortized Premium 2,781 2,757
Accretable Purchase Discount (657,248) (676,033)
Credit Reserve Purchase Discount (712,017) (653,613)
Amortized Cost 2,441,235 2,431,245
Unrealized Gain 505,434 488,931
Unrealized Loss (3,757) (3,166)
Available-for-sale securities, at fair value 2,942,912 2,917,010
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Interest-Only-Strip [Member]    
Schedule of Available-for-sale Securities [Line Items]    
Principal/ Current Face 5,495,775 5,614,925
Unamortized Premium 73,619 65,667
Accretable Purchase Discount 0 0
Credit Reserve Purchase Discount 0 0
Amortized Cost 73,619 65,667
Unrealized Gain 3,938 2,163
Unrealized Loss (3,256) (2,746)
Available-for-sale securities, at fair value $ 74,301 $ 65,084