| **Transfers Accounted for as Secured Borrowings (Details) - U.S. Government-sponsored mortgage-backed securities - USD ($) $ in Thousands** | Sep. 30, 2017 | Dec. 31, 2016 |
|---------------------------------------------------------------------------------------------------------------------------------------------|---------------|---------------|
| **Assets Sold under Agreements to Repurchase [Line Items]**                                                                                 |          |          |
| Collateral pledged for all repurchase agreements accounted for as secured borrowings                                                        | $ 142,107     | $ 146,480     |
| Overnight and Continuous                                                                                                                    |          |          |
| **Assets Sold under Agreements to Repurchase [Line Items]**                                                                                 |          |          |
| Collateral pledged for all repurchase agreements accounted for as secured borrowings                                                        | 129,128       | 129,617       |
| Up to 30 Days                                                                                                                               |          |          |
| **Assets Sold under Agreements to Repurchase [Line Items]**                                                                                 |          |          |
| Collateral pledged for all repurchase agreements accounted for as secured borrowings                                                        | 1,339         | 1,337         |
| 30-90 Days                                                                                                                                  |          |          |
| **Assets Sold under Agreements to Repurchase [Line Items]**                                                                                 |          |          |
| Collateral pledged for all repurchase agreements accounted for as secured borrowings                                                        | 2,544         | 10,253        |
| Greater Than 90 Days                                                                                                                        |          |          |
| **Assets Sold under Agreements to Repurchase [Line Items]**                                                                                 |          |          |
| Collateral pledged for all repurchase agreements accounted for as secured borrowings                                                        | $ 9,096       | $ 5,273       |

| 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.
+ References
No definition available.
+ Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseLineItems**Namespace Prefix:**us-gaap_**Data Type:**xbrli:stringItemType**Balance Type:**na**Period Type:**duration |
| X                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             |
|-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Definition
Carrying value, as of the balance sheet date, of securities sold under agreements to repurchase where the transferor maintains effective control over the assets, accounting for them as secured debt.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(m)(1)(i)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 10 -Section 55 -Paragraph 51 -URI http://asc.fasb.org/extlink&oid=77903054&loc=d3e101761-111710
+ Details**Name:**us-gaap_SecuredDebtRepurchaseAgreements**Namespace Prefix:**us-gaap_**Data Type:**xbrli:monetaryItemType**Balance Type:**credit**Period Type:**instant |
| X                                                                                                                                                                                                      |
|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseAxis=us-gaap_USGovernmentSponsoredEnterprisesDebtSecuritiesMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                        |
|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis=us-gaap_MaturityOvernightMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis=us-gaap_MaturityUpTo30DaysMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis=us-gaap_Maturity30To90DaysMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |
| X                                                                                                                                                                                         |
|-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| - Details**Name:**us-gaap_AssetsSoldUnderAgreementsToRepurchaseMaturityPeriodsAxis=us-gaap_MaturityOver90DaysMember**Namespace Prefix:****Data Type:**na**Balance Type:****Period Type:** |