| **SOI Proceeds from sales (Details) (USD $)In Thousands, unless otherwise specified** | 12 Months Ended                                                     |
|---------------------------------------------------------------------------------------|---------------------------------------------------------------------|
||
| **Investments, Debt and Equity Securities [Abstract]**                                |                                                                |  |   |  |   |  |
| Proceeds from sales                                                                   | $ 2,705,999us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt | [1] | $ 2,518,568us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt | [1] | $ 2,697,809us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt | [1] |
| Gross realized gains from sales                                                       | 47,852us-gaap_AvailableForSaleSecuritiesGrossRealizedGains          |  | 71,758us-gaap_AvailableForSaleSecuritiesGrossRealizedGains |  | 113,984us-gaap_AvailableForSaleSecuritiesGrossRealizedGains |  |
| Gross realized losses from sales                                                      | $ 1,229us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses        |  | $ 27,792us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses |  | $ 4,371us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses |  |
|                                                                                       |
| [1]Includes gains (losses) on the hedged asset for fair value hedges.                 |

| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the gross profit realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563
+ Details**Name:**us-gaap_AvailableForSaleSecuritiesGrossRealizedGains**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      |
|----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
This item represents the gross loss realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27357-111563
+ Details**Name:**us-gaap_AvailableForSaleSecuritiesGrossRealizedLosses**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |
| X                                                                                                                                                                              |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_InvestmentsDebtAndEquitySecuritiesAbstract**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           |
|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
The cash inflow associated with the sale of debt securities classified as available-for-sale securities.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Investing Activities -URI http://asc.fasb.org/extlink&oid=6516133Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26853-111562Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585
+ Details**Name:**us-gaap_ProceedsFromSaleOfAvailableForSaleSecuritiesDebt**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**debit**Period Type:**duration |