TWO Quarterly report pursuant to Section 13 or 15(d)

Available-for-sale Securities Classified by Rate Type (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, at fair value	$ 12,634,056	$ 12,256,727
Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Adjustable Rate	944,503	1,006,621
Available-for-sale Securities, Fixed Rate	8,879,422	8,490,788
Available-for-sale securities, at fair value	9,823,925	9,497,409
Mortgage-backed Securities, Issued by Private Enterprises [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Adjustable Rate	2,449,928	2,403,078
Available-for-sale Securities, Fixed Rate	360,203	356,240
Available-for-sale securities, at fair value	2,810,131	2,759,318
Collateralized Mortgage Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Adjustable Rate	3,394,431	3,409,699
Available-for-sale Securities, Fixed Rate	9,239,625	8,847,028
Available-for-sale securities, at fair value	$ 12,634,056	$ 12,256,727