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Commitments, Contingencies and Related Party Transactions (Narrative) (Details) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | ---
Guarantees |  |
Commercial letters of credit and SBLCs | $ 1,655,897 | $ 1,525,613
Maximum potential future payments up to recourse component | 38,700 | 46,400
Other Commitments |  |
Unfunded commitments for investments in AHP and other tax credit investments | 169,187 |
Accrued Expenses and Other Liabilities |  |
Guarantees |  |
Allowance for unfunded credit reserves | 12,700 | 15,700
Other Commitments |  |
Unfunded commitments for investments in AHP and other tax credit investments | 169,200 | 174,300
Single Family Residential and Multi-Family Residential | Loans Sold or Securitized with Recourse |  |
Guarantees |  |
Principal amount outstanding on loans sold or securitized | 113,700 | 150,500
Single Family Residential and Multi-Family Residential | Loans Sold or Securitized with Recourse | Accrued Expenses and Other Liabilities |  |
Guarantees |  |
Allowance for unfunded credit reserves | 214 | $ 373
Standby Letters of Credit |  |
Guarantees |  |
Commercial letters of credit and SBLCs | 1,600,000 |
Commercial Letters Of Credit |  |
Guarantees |  |
Commercial letters of credit and SBLCs | $ 55,700 |

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- Definition The current carrying amount of the liability for the freestanding or embedded guarantor's obligations under the guarantee or each group of similar guarantees. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248 + Details
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- Definition Maximum potential amount of future payments (undiscounted) the guarantor could be required to make under the guarantee or each group of similar guarantees before reduction for potential recoveries under recourse or collateralization provisions. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 4 -Subparagraph (b)(1) -URI http://asc.fasb.org/extlink&oid=82913245&loc=d3e12069-110248 + Details
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- Definition Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions. + References No definition available. + Details
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