Annual report pursuant to Section 13 and 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
Dec. 31, 2013
Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]    
Available-for-Sale Securities, Number of Positions 1,431 1,493
Available-for-Sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Number of Positions 447 250
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Number of Positions 114 47
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value $ 4,902,813 $ 2,548,995
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Percent Agency 96.90% 95.80%
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Unrealized Losses (171,651) (18,610)
Available-for-sale Securities, Continuous Unrealized Loss Position, Twelve Months or Longer, Fair Value 1,186,692 52,689
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 Months or Longer, Unrealized Losses (81,393) (9,628)
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value 6,089,505 2,601,684
Available-for-sale Securities, Continuous Unrealized Loss Position, Unrealized Losses (253,044) (28,238)
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 $ 4,752,861 $ 2,440,929