Available-for-sale Securities Classified by Rate Type (Details) - USD ($) $ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Available-for-sale Securities, Adjustable Rate | $ 1,578,431 | $ 1,781,634 |
| Available-for-sale Securities, Fixed Rate | 12,706,194 | 6,043,686 |
| Available-for-sale Securities | 14,284,625 | 7,825,320 |
| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Available-for-sale Securities, Adjustable Rate | 32,588 | 108,596 |
| Available-for-sale Securities, Fixed Rate | 12,404,228 | 5,864,294 |
| Available-for-sale Securities | 12,436,816 | 5,972,890 |
| Mortgage-backed Securities, Issued by Private Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Available-for-sale Securities, Adjustable Rate | 1,545,843 | 1,673,038 |
| Available-for-sale Securities, Fixed Rate | 301,966 | 179,392 |
| Available-for-sale Securities | $ 1,847,809 | $ 1,852,430 |
| X | ||||||||||
- Definition This item represents investments in debt and equity securities with adjustable coupon rates which are categorized neither as held-to-maturity nor trading. No definition available.
|
| X | ||||||||||
- Definition This item represents investments in debt and equity securities with fixed coupon rates which are categorized neither as held-to-maturity nor trading. No definition available.
|
| X | ||||||||||
- Definition Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|