Available-for-sale Securities Classified by Rate Type (Details) - USD ($) $ in Thousands |
Dec. 31, 2016 |
Dec. 31, 2015 |
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| Schedule of Available-for-sale Securities [Line Items] | ||
| Available-for-sale Securities, Adjustable Rate | $ 1,605,313 | $ 1,781,634 |
| Available-for-sale Securities, Fixed Rate | 11,523,544 | 6,043,686 |
| Available-for-sale Securities | 13,128,857 | 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 | 30,463 | 108,596 |
| Available-for-sale Securities, Fixed Rate | 11,196,011 | 5,864,294 |
| Available-for-sale Securities | 11,226,474 | 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 | 1,574,850 | 1,673,038 |
| Available-for-sale Securities, Fixed Rate | 327,533 | 179,392 |
| Available-for-sale Securities | $ 1,902,383 | $ 1,852,430 |
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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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