Available-for-sale Securities Classified by Rate Type (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | $ 2,645,930 | $ 1,592,627 |
| Fixed Rate | 18,574,889 | 11,523,544 |
| Available-for-sale securities, at fair value | 21,220,819 | 13,116,171 |
| Mortgage-backed Securities, Issued by US Government Sponsored Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | 23,220 | 30,463 |
| Fixed Rate | 18,215,505 | 11,196,011 |
| Available-for-sale securities, at fair value | 18,238,725 | 11,226,474 |
| Mortgage-backed Securities, Issued by Private Enterprises [Member] | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Adjustable Rate | 2,622,710 | 1,562,164 |
| Fixed Rate | 359,384 | 327,533 |
| Available-for-sale securities, at fair value | $ 2,982,094 | $ 1,889,697 |
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- 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.
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- 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.
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- 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
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- 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.
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