Available-for-sale Securities Classified by Rate Type (Details) - USD ($) $ in Thousands |
Sep. 30, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | $ 2,325,207 | $ 1,605,313 |
| Fixed Rate | 17,873,887 | 11,523,544 |
| Available-for-sale securities, at fair value | 20,199,094 | 13,128,857 |
| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | 24,960 | 30,463 |
| Fixed Rate | 17,529,411 | 11,196,011 |
| Available-for-sale securities, at fair value | 17,554,371 | 11,226,474 |
| Mortgage-backed Securities, Issued by Private Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | 2,300,247 | 1,574,850 |
| Fixed Rate | 344,476 | 327,533 |
| Available-for-sale securities, at fair value | $ 2,644,723 | $ 1,902,383 |
| 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
|