Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Available-for-Sale Securities, at Fair Value Schedule of Unrealized Loss on Investments (Details) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2014
Dec. 31, 2013
Schedule of Available-for-sale Securities [Line Items]    
Available-for-Sale Securities, Number of Positions 1,480 1,431
Available-for-Sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions 400 447
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions 125 114
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value $ 3,760,486 $ 4,902,813
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Percent Agency 97.20% 96.90%
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Losses (99,760) (171,651)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,012,554 1,186,692
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Aggregate Losses (56,070) (81,393)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value 4,773,040 6,089,505
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Losses (155,830) (253,044)
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
    
Schedule of Available-for-sale Securities [Line Items]    
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value $ 3,655,589 $ 4,752,861