Quarterly report pursuant to Section 13 or 15(d)

Available-for-Sale Securities, at Fair Value Schedule of Unrealized Loss on Investments (Details)

v3.10.0.1
Available-for-Sale Securities, at Fair Value Schedule of Unrealized Loss on Investments (Details)
$ in Thousands
Sep. 30, 2018
USD ($)
position
Dec. 31, 2017
USD ($)
position
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Number of Positions | position 1,605 1,435
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Number of Positions | position 522 253
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Number of Positions | position 361 234
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months $ 15,358,443 $ 12,198,870
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Percent Agency 96.60% 98.50%
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months, Accumulated Loss $ (309,999) $ (65,313)
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer 6,941,115 2,464,544
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, 12 Months or Longer, Accumulated Loss (417,352) (114,724)
Debt Securities, Available-for-sale, Unrealized Loss Position 22,299,558 14,663,414
Debt Securities, Available-for-sale, Unrealized Loss Position, Accumulated Loss (727,351) (180,037)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]    
Debt Securities, Available-for-sale [Line Items]    
Debt Securities, Available-for-sale, Continuous Unrealized Loss Position, Less than 12 Months $ 14,800,000 $ 12,000,000