| Summary of Significant Accounting Policies / Accounting Policies (Policies) | 12 Months Ended |
| Dec. 31, 2017 |
| Accounting Policies [Abstract] | |
| Use of Estimates, Policy [Policy Text Block] | The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make a number of judgments, estimates, and assumptions that may affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported amounts of income, expenses, gains, and losses during the reporting period. The most significant of these estimates include estimating the allowance for credit losses on the advances and mortgage loan portfolios; accounting for derivatives; estimating fair values of investments classified as trading and available-for-sale, derivatives and associated hedged items carried at fair value in accordance with the accounting for derivative instruments and associated hedging activities, and financial instruments carried at fair value under the fair value option, and accounting for other-than-temporary impairment (OTTI) for investment securities; and estimating the prepayment speeds on mortgage-backed securities (MBS) and mortgage loans for the accounting of amortization of premiums and accretion of discounts on MBS and mortgage loans. Actual results could differ significantly from these estimates. The preparation of financial statements in accordance with accounting principles generally accepted in the United States of America (U.S. GAAP) requires management to make a number of judgments, estimates, and assumptions that may affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities, and the reported amounts of income, expenses, gains, and losses during the reporting period. The most significant of these estimates include estimating the allowance for credit losses on the advances and mortgage loan portfolios; accounting for derivatives; estimating fair values of investments classified as trading and available-for-sale, derivatives and associated hedged items carried at fair value in accordance with the accounting for derivative instruments and associated hedging activities, and financial instruments carried at fair value under the fair value option, and accounting for other-than-temporary impairment (OTTI) for investment securities; and estimating the prepayment speeds on mortgage-backed securities (MBS) and mortgage loans for the accounting of amortization of premiums and accretion of discounts on MBS and mortgage loans. Actual results could differ significantly from these estimates. |
| Fair Value Measurement, Policy [Policy Text Block] | Many of the Bank's financial instruments lack an available liquid trading market as characterized by frequent exchange transactions between a willing buyer and willing seller. Therefore, the Bank uses financial models employing significant assumptions and present value calculations for the purpose of determining estimated fair values. Thus, the fair values may not represent the actual values of the financial instruments that could have been realized as of yearend or that will be realized in the future. Fair values for certain financial instruments are based on quoted prices, market rates, or replacement rates for similar financial instruments as of the last business day of the year. The estimated fair values of the Bank's financial instruments and related assumptions are detailed in Note 19 – Fair Value . |
| Reclassification, Policy [Policy Text Block] | |
| Repurchase and Resale Agreements Policy [Policy Text Block] | These investments provide short-term liquidity and are carried at cost. The Bank treats securities purchased under agreements to resell as collateralized financing arrangements because they effectively represent short-term loans to counterparties that are considered by the Bank to be of investment quality, which are classified as assets in the Statements of Condition. Securities purchased under agreements to resell are held in safekeeping in the name of the Bank by third-party custodians approved by the Bank. In accordance with the terms of these loans, if the market value of the underlying securities decreases below the market value required as collateral, the counterparty must place an equivalent amount of additional securities as collateral or remit an equivalent amount of cash. If an agreement to resell is deemed to be impaired, the difference between the fair value of the collateral and the amortized cost of the agreement is charged to earnings. |
| Investment, Policy [Policy Text Block] | Federal Funds Sold. These investments provide short-term liquidity and are carried at cost. The Bank invests in Federal funds sold with counterparties that are considered by the Bank to be of investment quality. Interest-bearing Deposits. This investment provides short-term liquidity and is carried at cost. Interest-bearing deposits include interest-bearing deposits in banks not meeting the definition of a security. Interest income on interest-bearing deposits is accrued as earned and recorded in interest income on the Statements of Income. Investment Securities. The Bank classifies investments as trading, available-for-sale (AFS), or held-to-maturity (HTM) at the date of acquisition. Purchases and sales of securities are recorded on a trade date basis. The Bank classifies certain investments as trading. These securities are held for liquidity purposes and carried at fair value with changes in the fair value of these investments recorded in other income. The Bank does not participate in speculative trading practices and holds these investments indefinitely as the Bank periodically evaluates its liquidity needs. The Bank classifies certain securities as AFS and carries these securities at their fair value. Unrealized gains and losses on these securities are recognized in accumulated other comprehensive income (AOCI). HTM securities are carried at cost, adjusted for periodic principal repayments; amortization of premiums and accretion of discounts; and previous OTTI recognized in net income and AOCI. The Bank classifies these investments as HTM securities because the Bank has the positive intent and ability to hold these securities until maturity. Certain changes in circumstances may cause the Bank to change its intent to hold a certain security to maturity without calling into question its intent to hold other debt securities to maturity in the future. Thus, the sale or transfer of an HTM security because of certain changes in circumstances, such as evidence of significant deterioration in the issuer's creditworthiness or changes in regulatory requirements, is not considered to be inconsistent with its original classification. Other events that are isolated, nonrecurring, and unusual for the Bank that could not have been reasonably anticipated may cause the Bank to sell or transfer an HTM security without necessarily calling into question its intent to hold other debt securities to maturity. In addition, sales of debt securities that meet either of the following two conditions may be considered as maturities for purposes of the classification of securities: (i) the sale occurs near enough to its maturity date (or call date if exercise of the call is probable) that interest rate risk is substantially eliminated as a pricing factor and changes in market interest rates would not have a significant effect on the security's fair value, or (ii) the sale occurs after the Bank has already collected a substantial portion (at least 85% ) of the principal outstanding at acquisition because of prepayments on the debt security or scheduled payments on a debt security payable in equal installments (both principal and interest) over its term. The Bank calculates the amortization of purchase premiums and accretion of purchase discounts on investments using the level-yield method on a retrospective basis over the estimated life of the securities. This method requires a retrospective adjustment of the effective yield each time the Bank changes the estimated life as if the new estimate had been known since the original acquisition date of the securities. The Bank uses nationally recognized, market-based, third-party prepayment models to project estimated lives. On a quarterly basis, the Bank evaluates its individual AFS and HTM investment securities in an unrealized loss position for OTTI. A security is considered impaired when its fair value is less than its amortized cost basis. For impaired debt securities, an entity is required to assess whether: (i) it has the intent to sell the debt security; (ii) it is more likely than not that it will be required to sell the debt security before its anticipated recovery of the remaining amortized cost basis of the security; or (iii) it does not expect to recover the entire amortized cost basis of the impaired debt security. If any of these conditions is met, an OTTI on the security must be recognized. With respect to any debt security, a credit loss is defined as the amount by which the amortized cost basis exceeds the present value of the cash flows expected to be collected. If a credit loss exists but the entity does not intend to sell the debt security and it is not more likely than not that the entity will be required to sell the debt security before the anticipated recovery of its remaining amortized cost basis (the amortized cost basis less any current-period credit loss), the carrying value of the debt security is adjusted to its fair value. However, instead of recognizing the entire difference between the amortized cost basis and fair value in earnings, only the amount of the impairment representing the credit loss is recognized in earnings, while the amount of non-credit-related impairment is recognized in AOCI. The total OTTI is presented in the Statements of Income with an offset for the amount of the total OTTI that is recognized in AOCI. This presentation provides additional information about the amounts that the entity does not expect to collect related to a debt security. The credit loss on a debt security is limited to the amount of that security's unrealized losses. For subsequent accounting of other-than-temporarily impaired securities, if the present value of cash flows expected to be collected is less than the amortized cost basis, the Bank records an additional OTTI. The amount of total OTTI for a security that was previously impaired is calculated as the difference between its amortized cost less the amount of OTTI recognized in AOCI prior to the determination of OTTI and its fair value. For an other-than-temporarily impaired security that was previously impaired and has subsequently incurred an additional OTTI related to credit loss (limited to that security's unrealized losses), this additional credit-related OTTI, up to the amount in AOCI, would be reclassified out of non-credit-related OTTI in AOCI and charged to earnings. Any credit loss in excess of the related AOCI is charged to earnings. Subsequent related increases and decreases (if not an OTTI) in the fair value of AFS securities will be netted against the non-credit component of OTTI previously recognized in AOCI. For securities classified as HTM, the OTTI recognized in AOCI is accreted to the carrying value of each security on a prospective basis, based on the amount and timing of future estimated cash flows (with no effect on earnings unless the security is subsequently sold or there are additional decreases in cash flows expected to be collected). For securities classified as AFS, the Bank does not accrete the OTTI recognized in AOCI to the carrying value because the subsequent measurement basis for these securities is fair value. For securities previously identified as other-than-temporarily impaired, the Bank updates its estimate of future estimated cash flows on a regular basis. If there is no additional impairment on the security, any improvement in expected cash flows is accreted into interest income in the Statements of Income. To assess whether it expects to recover the entire amortized cost basis of its PLRMBS, the Bank performed a cash flow analysis for all of its PLRMBS as of December 31, 2017 , using two third-party models. The OTTI Governance Committee of the Federal Home Loan Banks (FHLBanks) developed a short-term housing price forecast with projected changes ranging from a decrease of 5.0% to an increase of 12.0% over the 12-month period beginning October 1, 2017 . For the vast majority of markets, the projected short-term housing price changes range from an increase of 2.0% to an increase of 6.0% . Thereafter, a unique path is projected for each geographic area based on an internally developed framework derived from historical data. The projected cash flows are based on a number of assumptions and expectations, and the results of these models can vary significantly with changes in assumptions and expectations. The scenario of cash flows determined reflects a best-estimate scenario and includes a base case housing price forecast that reflects the expectations for near- and long-term housing price behavior. At each quarter end, the Bank compares the present value of the cash flows expected to be collected on its PLRMBS to the amortized cost basis of the securities to determine whether a credit loss exists. The Bank then uses the effective interest rate for the security prior to impairment for determining the present value of the future estimated cash flows. For all the PLRMBS in its AFS and HTM portfolios, the Bank does not intend to sell any security and it is not more likely than not that the Bank will be required to sell any security before its anticipated recovery of the remaining amortized cost basis. Changes in circumstances may cause the Bank to change its intent to hold a certain security to maturity without calling into question its intent to hold other debt securities to maturity in the future. The sale or transfer of an HTM security because of certain changes in circumstances, such as evidence of significant deterioration in the issuers’ creditworthiness, is not considered to be inconsistent with its original classification. In addition, other events that are isolated, nonrecurring, or unusual for the Bank that could not have been reasonably anticipated may cause the Bank to sell or transfer an HTM security without necessarily calling into question its intent to hold other debt securities to maturity. The Bank elected to transfer any PLRMBS that incurred a credit-related OTTI charge during the applicable period from the Bank’s held-to-maturity portfolio to its available-for-sale portfolio at their fair values. The Bank recognized an OTTI credit loss on these held-to-maturity PLRMBS, which the Bank believes is evidence of a significant decline in the issuers’ creditworthiness. The decline in the issuers’ creditworthiness is the basis for the transfers to the available-for-sale portfolio. These transfers allow the Bank the option to sell these securities prior to maturity in view of changes in interest rates, changes in prepayment risk, or other factors, while recognizing the Bank’s intent to hold these securities for an indefinite period of time. The Bank does not intend to sell its other-than-temporarily impaired securities and it is not more likely than not that the Bank will be required to sell any security before its anticipated recovery of the remaining amortized cost basis. |
| Derivatives, Offsetting Fair Value Amounts, Policy [Policy Text Block] | The Bank presents certain financial instruments, including derivative instruments and securities purchased under agreements to resell, on a net basis when they have a legal right of offset and all other requirements for netting are met (collectively referred to as the netting requirements). The Bank has elected to offset its derivative asset and liability positions, as well as cash collateral received or pledged, when the netting requirements are met. The Bank did not have any offsetting liabilities related to its securities purchased under agreements to resell for the periods presented. The net exposure for these financial instruments can change on a daily basis; therefore, there may be a delay between the time this exposure change is identified and additional collateral is requested, and the time this collateral is received or pledged. Likewise, there may be a delay for excess collateral to be returned. For derivative instruments that meet the netting requirements, any excess cash collateral received or pledged is recognized as a derivative liability or derivative asset. Additional information regarding these agreements is provided in Note 18 – Derivatives and Hedging Activities . Based on the fair value of the related collateral held, the securities purchased under agreements to resell were fully collateralized for the periods presented. The Bank presents certain financial instruments, including derivative instruments and securities purchased under agreements to resell, on a net basis when they have a legal right of offset and all other requirements for netting are met (collectively referred to as the netting requirements). The Bank has elected to offset its derivative asset and liability positions, as well as cash collateral received or pledged, when the netting requirements are met. The Bank did not have any offsetting liabilities related to its securities purchased under agreements to resell for the periods presented. The net exposure for these financial instruments can change on a daily basis; therefore, there may be a delay between the time this exposure change is identified and additional collateral is requested, and the time this collateral is received or pledged. Likewise, there may be a delay for excess collateral to be returned. For derivative instruments that meet the netting requirements, any excess cash collateral received or pledged is recognized as a derivative liability or derivative asset. Additional information regarding these agreements is provided in Note 18 – Derivatives and Hedging Activities . Based on the fair value of the related collateral held, the securities purchased under agreements to resell were fully collateralized for the periods presented. The Bank may present derivative instruments, related cash collateral received or pledged, and associated accrued interest by clearing agent or by counterparty when the netting requirements have been met. |
| Consolidation, Variable Interest Entity, Policy [Policy Text Block] | The Bank’s investments in variable interest entities (VIEs) are limited to private-label residential mortgage-backed securities (PLRMBS). On an ongoing basis, the Bank performs a quarterly evaluation to determine whether it is the primary beneficiary in any VIE. The Bank evaluated its investments in VIEs as of December 31, 2017 , to determine whether it is a primary beneficiary of any of these investments. The primary beneficiary is required to consolidate a VIE. The Bank determined that consolidation accounting is not required because the Bank is not the primary beneficiary of these VIEs for the periods presented. The Bank does not have the power to significantly affect the economic performance of any of these investments because it does not act as a key decision maker nor does it have the unilateral ability to replace a key decision maker. In addition, the Bank does not design, sponsor, transfer, service, or provide credit or liquidity support in any of its investments in VIEs. The Bank’s maximum loss exposure for these investments is limited to the carrying value. The Bank’s investments in variable interest entities (VIEs) are limited to private-label residential mortgage-backed securities (PLRMBS). On an ongoing basis, the Bank performs a quarterly evaluation to determine whether it is the primary beneficiary in any VIE. The Bank evaluated its investments in VIEs as of December 31, 2017 , to determine whether it is a primary beneficiary of any of these investments. The primary beneficiary is required to consolidate a VIE. The Bank determined that consolidation accounting is not required because the Bank is not the primary beneficiary of these VIEs for the periods presented. The Bank does not have the power to significantly affect the economic performance of any of these investments because it does not act as a key decision maker nor does it have the unilateral ability to replace a key decision maker. In addition, the Bank does not design, sponsor, transfer, service, or provide credit or liquidity support in any of its investments in VIEs. The Bank’s maximum loss exposure for these investments is limited to the carrying value. |
| Federal Home Loan Bank, Advances, Receivables Policy [Policy Text Block] | The Bank reports advances (loans to members, former members or their successors, or housing associates) either at amortized cost or at fair value when the fair value option is elected. Advances carried at amortized cost are reported net of premiums, discounts (including discounts related to the Affordable Housing Program), and hedging adjustments. The Bank amortizes premiums and accretes discounts and recognizes hedging adjustments resulting from the discontinuation of a hedging relationship to interest income using a level-yield methodology. Interest on advances is credited to income as earned. For advances carried at fair value, the Bank recognizes contractual interest in interest income. Advance Modifications. In cases in which the Bank funds an advance concurrent with or within a short period of time before or after the prepayment of a previous advance to the same member, the Bank evaluates whether the subsequent advance meets the accounting criteria to qualify as a modification of an existing advance or whether it constitutes a new advance. The Bank compares the present value of the cash flows on the subsequent advance to the present value of the cash flows remaining on the previous advance. If there is at least a 10% difference in the present value of the cash flows or if the Bank concludes that the difference between the advances is more than minor based on a qualitative assessment of the modifications made to the previous advance's contractual terms, then the subsequent advance is accounted for as a new advance. In all other instances, the subsequent advance is accounted for as a modification. Prepayment Fees. When a borrower prepays certain advances prior to the original maturity, the Bank may charge the borrower a prepayment fee. For certain advances with partial prepayment symmetry, the Bank may charge the borrower a prepayment fee or pay the borrower a prepayment credit, depending on certain circumstances, such as movements in interest rates, when the advance is prepaid. For prepaid advances that are hedged and meet the hedge accounting requirements, the Bank terminates the hedging relationship upon prepayment and records the associated fair value gains and losses, adjusted for the prepayment fees, in interest income. If a new advance represents a modification of an original hedged advance, the fair value gains or losses on the advance and the prepayment fees are included in the carrying amount of the modified advance, and gains or losses and prepayment fees are amortized in interest income over the life of the modified advance using the level-yield method. If the modified advance is also hedged and the hedge meets the hedge accounting requirements, the modified advance is marked to fair value after the modification, and subsequent fair value changes are recorded in other income. If the prepayment represents an extinguishment of the original hedged advance, the prepayment fee and any fair value gain or loss are immediately recognized in interest income. For prepaid advances that are not hedged or that are hedged but do not meet the hedge accounting requirements, the Bank records prepayment fees in interest income unless the Bank determines that the new advance represents a modification of the original advance. If the new advance represents a modification of the original advance, the prepayment fee on the original advance is deferred, recorded in the basis of the modified advance, and amortized over the life of the modified advance using the level-yield method. This amortization is recorded in interest income. The Bank charges borrowers prepayment fees or pays borrowers prepayment credits when the principal on certain advances is paid prior to original maturity. The Bank records prepayment fees net of any associated fair value adjustments related to prepaid advances that were hedged. The net amount of prepayment fees is reflected as interest income in the Statements of Income |
| Loans and Leases Receivable, Mortgage Banking Activities, Policy [Policy Text Block] | Under the Mortgage Partnership Finance® (MPF®) Program, the Bank may purchase from members, for its own portfolio, conventional conforming fixed rate residential mortgage loans under the MPF Original product and mortgage loans insured by the Federal Housing Administration (FHA) or guaranteed by the Department of Veterans Affairs (VA) from its participating members under the MPF Government product. (“Mortgage Partnership Finance” and “MPF” are registered trademarks of the FHLBank of Chicago.) Participating members originate or purchase the mortgage loans, credit-enhance them and sell them to the Bank, and generally retain the servicing of the loans. The Bank manages the interest rate risk, prepayment risk, and liquidity risk of each loan in its portfolio. The Bank and the participating financial institution (either the original participating member that sold the loans to the Bank or a successor to that member) share in the credit risk of the loans, with the Bank assuming the first loss obligation limited by the first loss account, and the participating financial institution assuming credit losses in excess of the first loss account, up to the amount of the credit enhancement obligation specified in the master agreement. The amount of the credit enhancement is calculated so that any Bank credit losses (excluding special hazard losses) in excess of the first loss account are limited to those that would be expected from an equivalent investment with a long-term credit rating of AA for loans purchased prior to April 2017 and BBB for loans purchased thereafter, as determined by the MPF Program methodology. In addition, the Bank may facilitate the purchase of conforming fixed rate mortgage loans from members for concurrent sale to Fannie Mae under the MPF Xtra® product; of jumbo fixed rate mortgage loans for concurrent sale to Redwood Residential Acquisition Corporation, a subsidiary of Redwood Trust, Inc., a real estate investment trust, under the MPF Direct product; and of government-insured or government-guaranteed mortgage loans that will be packaged into securities backed by the mortgage loans and guaranteed by Ginnie Mae under the MPF Government MBS product. When members sell mortgage loans under the MPF Xtra, MPF Direct, and MPF Government MBS products, the loans are sold to a third-party investor and are not recorded on the Bank’s Statements of Condition. (“MPF Xtra” is a registered trademark of the FHLBank of Chicago.) Under the MPF® Program, the Bank may purchase from members, for its own portfolio, conventional conforming fixed rate mortgage loans under the MPF Original product and mortgage loans insured by the FHA or guaranteed by the Department of VA under the MPF Government product. In addition, the Bank may facilitate the purchase of conforming fixed rate mortgage loans from members for concurrent sale to Fannie Mae under the MPF Xtra® product; of jumbo fixed rate mortgage loans for concurrent sale to Redwood Residential Acquisition Corporation, a subsidiary of Redwood Trust, Inc., a real estate investment trust, under the MPF Direct product; and of government-insured or government-guaranteed mortgage loans that will be packaged into securities backed by the mortgage loans and guaranteed by Ginnie Mae under the MPF Government MBS product. When members sell mortgage loans under the MPF Xtra, MPF Direct, and MPF Government MBS products, the loans are sold to a third-party investor and are not recorded on the Bank’s Statements of Condition. |
| Finance, Loan and Lease Receivables, Held-for-investment, Policy [Policy Text Block] | For taking on the credit enhancement obligation, the Bank pays the participating financial institution a credit enhancement fee, which is calculated on the remaining unpaid principal balance of the mortgage loans. Depending on the specific MPF product, all or a portion of the credit enhancement fee is typically paid monthly beginning with the month after each delivery of loans. The MPF Original product provides participating financial institutions the option to receive credit enhancement fees on a monthly basis or in an upfront lump sum amount that is included in the purchase price at the time loans are sold to the Bank. The lump sum amount is approximately equivalent to the present value of the monthly credit enhancement fees that the Bank would otherwise be expected to pay over the life of the loans. The MPF Plus product provides for a performance-based credit enhancement fee, which accrues monthly, beginning with the month after each delivery of loans, and is paid to the participating financial institution beginning 12 months later. The performance-based credit enhancement fee will be reduced by an amount equivalent to loan losses up to the amount of the first loss account established for each master commitment. The participating financial institutions obtain supplemental mortgage insurance (SMI) to cover their credit enhancement obligations under this product. If the SMI provider's claims-paying ability rating falls below a specified level, the participating financial institution has six months to either replace the SMI policy or assume the credit enhancement obligation and fully collateralize the obligation; otherwise the Bank may choose not to pay the participating financial institution its performance-based credit enhancement fee. The Bank classifies mortgage loans as held for investment and, accordingly, reports them at their principal amount outstanding net of unamortized premiums, unamortized credit enhancement fees paid as a lump sum at the time loans are purchased, discounts, and unrealized gains and losses from loans initially classified as mortgage loan commitments. The Bank defers and amortizes these amounts as interest income using the level-yield method on a retrospective basis over the estimated life of the related mortgage loan. Actual prepayment experience and estimates of future principal prepayments are used in calculating the estimated life of the mortgage loans. The Bank aggregates the mortgage loans by similar characteristics (type, maturity, note rate, and acquisition date) in determining prepayment estimates. A retrospective adjustment is required each time the Bank changes the estimated amounts as if the new estimate had been known since the original acquisition date of the assets. The Bank uses nationally recognized, market-based, third-party prepayment models to project estimated lives. The Bank records credit enhancement fees as a reduction to interest income. |
| Loans and Leases Receivable, Allowance for Loan Losses Policy [Policy Text Block] | An allowance for credit losses is a valuation allowance separately established for each identified portfolio segment, if it is probable that impairment has occurred in the Bank's portfolio as of the Statements of Condition date and the amount of loss can be reasonably estimated. To the extent necessary, an allowance for credit losses for off-balance sheet credit exposures is recorded as a liability. Portfolio Segments. A portfolio segment is defined as the level at which an entity develops and documents a systematic method for determining its allowance for credit losses. The Bank has developed and documented a systematic methodology for determining an allowance for credit losses for each applicable portfolio segment. See Note 10 – Allowance for Credit Losses for more information. The Bank invests in Federal funds sold with counterparties that are considered by the Bank to be of investment quality, and these investments are evaluated for purposes of an allowance for credit losses only if the investment is not paid when due The Bank and any participating financial institution share in the credit risk of the loans sold by that institution as specified in a master agreement. Loans purchased under the MPF Program generally had a credit risk exposure at the time of purchase that, as determined by the MPF Program methodology, would be expected from an equivalent investment rated AA if purchased prior to April 2017, or rated BBB if purchased since April 2017, taking into consideration the credit risk sharing structure mandated by the Finance Agency’s acquired member assets (AMA) regulation. The MPF Program structures potential credit losses on conventional MPF loans into layers with respect to each pool of loans purchased by the Bank under a single master commitment, as follows: 1. The first layer of protection against loss is the liquidation value of the real property securing the loan. 2. The next layer of protection comes from the primary mortgage insurance that is required for loans with a loan-to-value ratio greater than 80% , if still in place. 3. Losses that exceed the liquidation value of the real property and any primary mortgage insurance, up to an agreed-upon amount called the first loss account for each master commitment, are incurred by the Bank. 4. Losses in excess of the first loss account for each master commitment, up to an agreed-upon amount called the credit enhancement amount, are covered by the participating financial institution’s credit enhancement obligation at the time losses are incurred. 5. Losses in excess of the first loss account and the participating financial institution’s remaining credit enhancement for the master commitment, if any, are incurred by the Bank. The Bank calculates its estimated allowance for credit losses on mortgage loans acquired under the MPF Original and MPF Plus products as described below. Effective January 1, 2015, the Bank implemented the accounting requirements of regulatory Advisory Bulletin 2012-02. As a result, for any mortgage loans that are more than 180 days past due and that have any outstanding balance in excess of the fair value of the property, less cost to sell, this excess is charged off as a loss by the end of the month in which the applicable time period elapses. Likewise, when a borrower is in bankruptcy, loans are written down to the fair value of the collateral, less cost to sell, in general within 60 days of receipt of the notification of filing from the bankruptcy court, unless it can be clearly demonstrated and documented that repayment is likely to occur. As a result of these charge-offs, corresponding Allowance for Credit Losses on MPF Loans, which had previously provided for most of these expected losses, was reduced accordingly. Allowance for Credit Losses on MPF Loans – The Bank evaluates the allowance for credit losses on MPF mortgage loans based on two components. The first component applies to each individual loan that is specifically identified as impaired. The Bank evaluates the exposure on these loans by considering the first layer of loss protection (the liquidation value of the real property securing the loan) and the availability and collectability of credit enhancements under the terms of each master commitment and records a provision for credit losses. The second component applies to loans that are not specifically identified as impaired and is based on the Bank’s estimate of probable credit losses on those loans as of the financial statement date. The Bank evaluates the credit loss exposure on a loan pool basis considering various observable data, such as delinquency statistics, past performance, current performance, loan portfolio characteristics, collateral valuations, industry data, and prevailing economic conditions. The Bank also considers the availability and collectability of credit enhancements from participating financial institutions or from mortgage insurers under the terms of each master commitment. |
| Finance, Loan and Lease Receivables, Held-for-investment, Allowance and Nonperforming Loans, Allowance Policy [Policy Text Block] | A mortgage loan is considered impaired when, based on current information and events, it is probable that the Bank will be unable to collect all amounts due according to the contractual terms of the mortgage loan agreement. Loans that are on non-accrual status and that are considered collateral-dependent are measured for impairment based on the fair value of the underlying property less estimated selling costs. Loans are considered collateral-dependent if repayment is expected to be provided solely by the sale of the underlying property, that is, there is no other available and reliable source of repayment. Collateral-dependent loans are impaired if the fair value of the underlying collateral less estimated selling costs is insufficient to recover the unpaid principal balance on the loan. Interest income on impaired loans is recognized in the same manner as interest income on non-accrual loans noted below. The Bank places a mortgage loan on nonaccrual status when the collection of the contractual principal or interest from the participating financial institution is reported 90 days or more past due or when the loan is in foreclosure. When a mortgage loan is placed on nonaccrual status, accrued but uncollected interest is reversed against interest income. The Bank records cash payments received on nonaccrual loans first as interest income and then as a reduction of principal as specified in the contractual agreement, unless the collection of the remaining principal amount due is considered doubtful. If the collection of the remaining principal amount due is considered doubtful, then cash payments received would be applied first solely to principal until the remaining principal amount due is expected to be collected and then as a recovery of any charge-off, if applicable, followed by recording interest income. A loan on non-accrual status may be restored to accrual when (1) none of its contractual principal and interest is due and unpaid, and the Bank expects repayment of the remaining contractual interest and principal, or (2) it otherwise becomes well secured and in the process of collection. For any mortgage loans that are more than 180 days past due and that have any outstanding balance in excess of the fair value of the property, less cost to sell, this excess is charged off as a loss by the end of the month in which the applicable time period elapses. Likewise, when a borrower is in bankruptcy, loans are written down to the fair value of the collateral, less cost to sell, in general within 60 days of receipt of the notification of filing from the bankruptcy court, unless it can be clearly demonstrated and documented that repayment is likely to occur. A mortgage loan is considered to be impaired when it is reported 90 days or more past due (nonaccrual) or when it is probable, based on current information and events, that the Bank will be unable to collect all principal and interest amounts due according to the contractual terms of the mortgage loan agreement. Loans that are on nonaccrual status and that are considered collateral-dependent are measured for impairment based on the fair value of the underlying property less estimated selling costs. Loans are considered collateral-dependent if repayment is expected to be provided solely by the sale of the underlying property, that is, if it is considered likely that the borrower will default and there is no credit enhancement to offset losses under the master commitment, or the collectability or availability of credit enhancement is deemed to be uncertain. Collateral-dependent loans are impaired if the fair value of the underlying collateral less estimated selling costs is insufficient to recover the unpaid principal balance on the loan. Interest income on impaired loans is recognized in the same manner as interest income on nonaccrual loans, as noted below. The Bank places a mortgage loan on nonaccrual status when the collection of the contractual principal or interest from the participating financial institution is reported 90 days or more past due or when the loan is in foreclosure. When a mortgage loan is placed on nonaccrual status, accrued but uncollected interest is reversed against interest income. The Bank records cash payments received on nonaccrual loans first as interest income and then as a reduction of principal as specified in the contractual agreement, unless the collection of the remaining principal amount due is considered doubtful. An allowance for credit losses is a valuation allowance separately established for each identified portfolio segment, if it is probable that impairment has occurred in the Bank's portfolio as of the Statements of Condition date and the amount of loss can be reasonably estimated. To the extent necessary, an allowance for credit losses for off-balance sheet credit exposures is recorded as a liability. Portfolio Segments. A portfolio segment is defined as the level at which an entity develops and documents a systematic method for determining its allowance for credit losses. The Bank has developed and documented a systematic methodology for determining an allowance for credit losses for each of the following portfolio segments: • advances, letters of credit, and other extensions of credit, collectively referred to as “credit products,” • MPF loans held for portfolio, • term securities purchased under agreements to resell, and • term Federal funds sold. Classes of Financing Receivables. Classes of financing receivables generally are a disaggregation of a portfolio segment to the extent needed to understand the exposure to credit risk arising from these financing receivables. The Bank determined that no further disaggregation of the portfolio segments identified above is needed because the credit risk arising from these financing receivables is assessed and measured by the Bank at the portfolio segment level. Credit Products. The Bank lends to member financial institutions that have a principal place of business in Arizona, California, or Nevada. Under the FHLBank Act, the Bank is required to obtain sufficient collateral for credit products to protect the Bank from credit losses. Collateral eligible to secure credit products includes certain investment securities, residential mortgage loans, cash or deposits with the Bank, and other eligible real estate-related assets. The capital stock of the Bank owned by each borrowing member is pledged as additional collateral for the member's indebtedness to the Bank. The Bank may also accept secured small business, small farm, and small agribusiness loans, and securities representing a whole interest in such secured loans, as collateral from members that are community financial institutions. The Housing and Economic Recovery Act of 2008 (Housing Act) added secured loans for community development activities as collateral that the Bank may accept from community financial institutions. In addition, the Bank has advances outstanding to former members and member successors, which are also subject to these security terms. The Bank requires each borrowing member to execute a written Advances and Security Agreement, which describes the lending relationship between the Bank and the borrower. At December 31, 2017 and 2016 , the Bank had a perfected security interest in collateral pledged by each borrowing member, or by the member's affiliate on behalf of the member, and by each nonmember borrower, with an estimated value in excess of the outstanding credit products for that borrower. Based on the financial condition of the borrower, the Bank may either (i) allow the borrower or the pledging affiliate to retain physical possession of loan collateral pledged to the Bank, provided that the borrower or the pledging affiliate agrees to hold the collateral for the benefit of the Bank, or (ii) require the borrower or the pledging affiliate to deliver physical possession of loan collateral to the Bank or its custodial agent. All securities collateral is required to be delivered to the Bank's custodial agent. All loan collateral pledged to the Bank is subject to a UCC-1 financing statement. Section 10(e) of the FHLBank Act affords any security interest granted to the Bank by a member or any affiliate of the member or any nonmember borrower priority over claims or rights of any other party, except claims or rights that (i) would be entitled to priority under otherwise applicable law and (ii) are held by bona fide purchasers for value or secured parties with perfected security interests. The Bank classifies as impaired any advance with respect to which it is probable that all principal and interest due will not be collected according to its contractual terms. Impaired advances are valued using the present value of expected future cash flows discounted at the advance's effective interest rate, the advance's observable market price or, if collateral-dependent, the fair value of the advance's underlying collateral. When an advance is classified as impaired, the accrual of interest is discontinued and unpaid accrued interest is reversed. Advances do not return to accrual status until they are brought current with respect to both principal and interest and until the future principal payments are no longer in doubt. No advances were classified as impaired during the periods presented. The Bank manages its credit exposure related to credit products through an integrated approach that generally provides for a credit limit to be established for each borrower, includes an ongoing review of each borrower’s financial condition, and is coupled with conservative collateral and lending policies to limit the risk of loss while taking into account borrowers’ needs for a reliable funding source. The Bank manages its credit exposure related to credit products through an integrated approach that generally provides for a credit limit to be established for each borrower, includes an ongoing review of each borrower’s financial condition, and is coupled with conservative collateral and lending policies to limit the risk of loss while taking into account borrowers’ needs for a reliable funding source. At December 31, 2017 and 2016 , none of the Bank’s credit products were past due, on nonaccrual status, or considered impaired. There were no troubled debt restructurings related to credit products during December 31, 2017 and 2016 . |
| Finance, Loan and Lease Receivables, Held for Investments, Foreclosed Assets Policy [Policy Text Block] | Real estate owned (REO) includes assets that have been received in satisfaction of debt through foreclosures. REO is initially recorded at fair value less estimated selling costs and is subsequently carried at the lower of that amount or current fair value less estimated selling costs. The Bank recognizes a charge-off to the allowance for credit losses if the fair value of the REO less estimated selling costs is less than the recorded investment in the loan at the date of transfer from loans to REO. Any subsequent realized gains, realized or unrealized losses, and carrying costs are included in other non-interest expense in the Statements of Income. REO is recorded in “Other assets” in the Statements of Condition. At December 31, 2017 , the Bank’s other assets included $1 of REO resulting from foreclosure of 11 mortgage loans held by the Bank. At December 31, 2016 , the Bank’s other assets included $1 of REO resulting from foreclosure of 12 mortgage loans held by the Bank. |
| Derivatives, Policy [Policy Text Block] | All derivatives are recognized on the Statements of Condition at their fair value. The Bank has elected to report derivative assets and derivative liabilities net of cash collateral, including initial and variation margin, and accrued interest received from or pledged to futures commission merchants (clearing agents) or counterparties. The fair values of derivatives are netted by clearing agent or counterparty when the netting requirements have been met. If these netted amounts are positive, they are classified as an asset, and if negative, they are classified as a liability. Cash flows associated with derivatives are reflected as cash flows from operating activities in the Statements of Cash Flows unless the derivative meets the criteria to be a financing derivative. Each derivative is designated as one of the following: (1) a qualifying hedge of the change in fair value of (i) a recognized asset or liability or (ii) an unrecognized firm commitment (a fair value hedge); (2) a qualifying hedge of (i) a forecasted transaction or (ii) the variability of cash flows that are to be received or paid in connection with a recognized asset or liability (a cash flow hedge); (3) a non-qualifying hedge of an asset or liability for asset-liability management purposes or of certain advances and consolidated obligation bonds for which the Bank elected the fair value option (an economic hedge); or (4) a non-qualifying hedge of another derivative (an intermediation hedge) that is offered as a product to members or used to offset other derivatives with nonmember counterparties. If hedging relationships meet certain criteria, including but not limited to formal documentation of the hedging relationship and an expectation to be hedge effective, they are eligible for hedge accounting, and the offsetting changes in fair value of the hedged items attributable to the hedged risk may be recorded in earnings. The application of hedge accounting generally requires the Bank to evaluate the effectiveness of the hedging relationships at inception and on an ongoing basis and to calculate the changes in fair value of the derivatives and the related hedged items independently. This is known as the “long-haul” method of hedge accounting. Transactions that meet certain criteria qualify for the “short-cut” method of hedge accounting, in which an assumption can be made that the change in the fair value of a hedged item, because of changes in the benchmark rate, exactly offsets the change in the value of the related derivative. Under the shortcut method, the entire change in fair value of the interest rate swap is considered to be effective at achieving offsetting changes in fair values or cash flows of the hedged asset or liability. Derivatives are typically executed at the same time as the hedged item, and the Bank designates the hedged item in a qualifying hedge relationship as of the trade date. In many hedging relationships, the Bank may designate the hedging relationship upon its commitment to disburse an advance or trade a consolidated obligation in which settlement occurs within the shortest period of time possible for the type of instrument based on market settlement conventions. The Bank records the changes in the fair value of the derivatives and the hedged item beginning on the trade date. Changes in the fair value of a derivative that qualifies as a fair value hedge and is designated as a fair value hedge, along with changes in the fair value of the hedged asset or liability (hedged item) that are attributable to the hedged risk (including changes that reflect losses or gains on firm commitments), are recorded in other income as “Net gain/(loss) on derivatives and hedging activities.” Changes in the fair value of a derivative that qualifies as a cash flow hedge and is designated as a cash flow hedge, to the extent that the hedge is effective, are recorded in AOCI, a component of capital, until earnings are affected by the variability of the cash flows of the hedged transaction (until the periodic recognition of interest on a variable rate asset or liability is recorded in earnings). For both fair value and cash flow hedges, any hedge ineffectiveness (which represents the amount by which the change in the fair value of the derivative differs from the change in the fair value of the hedged item or the variability in the cash flows of the forecasted transaction) is recorded in other income as “Net gain/(loss) on derivatives and hedging activities.” Changes in the fair value of a derivative designated as an economic hedge or an intermediation hedge are recorded in current period earnings with no fair value adjustment to an asset or liability. An economic hedge is defined as a derivative hedging certain advances and consolidated obligation bonds for which the Bank elected the fair value option, or hedging specific or non-specific underlying assets, liabilities, or firm commitments, that does not qualify or was not designated for fair value or cash flow hedge accounting, but is an acceptable hedging strategy under the Bank's risk management program. These economic hedging strategies also comply with Finance Agency regulatory requirements prohibiting speculative hedge transactions. An economic hedge introduces the potential for earnings variability caused by the changes in fair value of the derivatives that are recorded in the Bank's income but are not offset by corresponding changes in the value of the economically hedged assets, liabilities, or firm commitments. The derivatives used in intermediary activities do not qualify for hedge accounting treatment and are separately marked to market through earnings. The net result of the accounting for these derivatives does not significantly affect the operating results of the Bank. Changes in the fair value of these non-qualifying hedges are recorded in other income as “Net gain/(loss) on derivatives and hedging activities.” In addition, the net settlements associated with these non-qualifying hedges are recorded in other income as “Net gain/(loss) on derivatives and hedging activities.” Cash flows associated with these stand-alone derivatives are reflected as cash flows from operating activities in the Statements of Cash Flows unless the derivative meets the criteria to be designated as a financing derivative. The net settlements of interest receivables and payables on derivatives designated as fair value or cash flow hedges are recognized as adjustments to the interest income or interest expense of the designated underlying hedged item. The net settlements of interest receivables and payables on intermediated derivatives for members and other economic hedges are recognized in other income as “Net gain/(loss) on derivatives and hedging activities.” The Bank discontinues hedge accounting prospectively when: (i) it determines that the derivative is no longer effective in offsetting changes in the fair value or cash flows of a hedged item (including hedged items such as firm commitments or forecasted transactions); (ii) the derivative and/or the hedged item expires or is sold, terminated, or exercised; (iii) it is no longer probable that the forecasted transaction will occur in the originally expected period; (iv) a hedged firm commitment no longer meets the definition of a firm commitment; (v) it determines that designating the derivative as a hedging instrument is no longer appropriate; or (vi) it decides to use the derivative to offset changes in the fair value of other derivatives or instruments carried at fair value. When hedge accounting is discontinued, the Bank either terminates the derivative or continues to carry the derivative on the Statements of Condition at its fair value, ceases to adjust the hedged asset or liability for changes in fair value, and amortizes the cumulative basis adjustment on the hedged item into earnings over the remaining life of the hedged item using a level-yield methodology. When hedge accounting is discontinued because the Bank determines that the derivative no longer qualifies as an effective cash flow hedge of an existing hedged item, the Bank continues to carry the derivative on the Statements of Condition at its fair value and reclassifies the AOCI adjustment into earnings when earnings are affected by the existing hedged item (the original forecasted transaction). Under limited circumstances, when the Bank discontinues cash flow hedge accounting because it is no longer probable that the forecasted transaction will occur by the end of the originally specified time period, or within the following two months, but it is probable the transaction will still occur in the future, the gain or loss on the derivative remains in AOCI and is recognized in earnings when the forecasted transaction affects earnings. However, if it is probable that a forecasted transaction will not occur by the end of the originally specified time period or within the following two months, the gains and losses that were recorded in AOCI are recognized immediately in earnings. When hedge accounting is discontinued because the hedged item no longer meets the definition of a firm commitment, the Bank continues to carry the derivative on the Statements of Condition at its fair value, removing from the Statements of Condition any asset or liability that was recorded to recognize the firm commitment and recording it as a gain or loss in current period earnings. The Bank may be the primary obligor on consolidated obligations and may make advances in which derivative instruments are embedded. Upon execution of these transactions, the Bank assesses whether the economic characteristics of the embedded derivative are clearly and closely related to the economic characteristics of the remaining component of the advance or debt (the host contract) and whether a separate, non-embedded instrument with the same terms as the embedded instrument would meet the definition of a derivative instrument. When it is determined that: (i) the embedded derivative has economic characteristics that are not clearly and closely related to the economic characteristics of the host contract, and (ii) a separate, stand-alone instrument with the same terms would qualify as a derivative instrument, the embedded derivative is separated from the host contract, carried at fair value, and designated as a stand-alone derivative instrument equivalent to an economic hedge. However, the entire contract is carried on the Statements of Condition at fair value and no portion of the contract is designated as a hedging instrument if the entire contract (the host contract and the embedded derivative) is to be measured at fair value, with changes in fair value reported in current period earnings (such as an investment security classified as trading, as well as hybrid financial instruments that are eligible for the fair value option), or if the Bank cannot reliably identify and measure the embedded derivative for purposes of separating the derivative from its host contract. The Bank is subject to credit risk as a result of potential nonperformance by counterparties to the interest rate exchange agreements. All of the Bank’s agreements governing uncleared derivative transactions contain master netting provisions to help mitigate the credit risk exposure to each counterparty. The Bank manages counterparty credit risk through credit analyses and collateral requirements and by following the requirements of the Bank’s risk management policies, credit guidelines, and Finance Agency and other regulations. The Bank also requires credit support agreements on all uncleared derivatives. For cleared derivatives, the clearinghouse is the Bank’s counterparty. The requirement that the Bank post initial and variation margin through a clearing agent, to the clearinghouse, exposes the Bank to institutional credit risk in the event that the clearing agent or the clearinghouse fails to meet its obligations. The use of cleared derivatives, however, mitigates the Bank’s overall credit risk exposure because a central counterparty is substituted for individual counterparties and variation margin is posted daily for changes in the value of cleared derivatives through a clearing agent. The Bank has analyzed the enforceability of offsetting rights applicable to its cleared derivative transactions and determined that the exercise of those offsetting rights by a non-defaulting party under these transactions should be upheld under applicable bankruptcy law and Commodity Futures Trading Commission rules in the event of a clearinghouse or clearing agent insolvency and under applicable clearinghouse rules upon a non-insolvency-based event of default of the clearinghouse or clearing agent. Based on this analysis, the Bank presents a net derivative receivable or payable for all of its transactions through a particular clearing agent with a particular clearinghouse. |
| Property, Plant and Equipment, Policy [Policy Text Block] | The Bank records premises, software, and equipment at cost less accumulated depreciation and amortization. The Bank's accumulated depreciation and amortization related to premises, software, and equipment totaled $74 and $61 at December 31, 2017 and 2016 , respectively. Improvements and major renewals are capitalized; ordinary maintenance and repairs are expensed as incurred. Depreciation is computed on the straight-line method over the estimated useful lives of assets ranging from 3 to 10 years , and leasehold improvements are amortized on the straight-line method over the estimated useful life of the improvement or the remaining term of the lease, whichever is shorter . |
| Internal Use Software, Policy [Policy Text Block] | The cost of computer software developed or obtained for internal use is capitalized and depreciated over future periods. |
| Debt, Policy [Policy Text Block] | Discounts and Premiums on Consolidated Obligations. The discounts on consolidated obligation discount notes for which the Bank is the primary obligor are amortized to expense using the level-yield method over the term to maturity. The discounts and premiums on consolidated obligation bonds for which the Bank is the primary obligor are amortized to expense using the level-yield method over the remaining contractual life or on a retrospective basis over the estimated life of the consolidated obligation bonds. Consolidated obligations are recorded at amortized cost unless the Bank has elected the fair value option, in which case the consolidated obligations are carried at fair value. Concessions on Consolidated Obligations. Concessions are paid to dealers in connection with the issuance of consolidated obligations for which the Bank is the primary obligor. The amount of the concession is allocated to the Bank by the Office of Finance based on the percentage of the debt issued for which the Bank is the primary obligor. Concessions paid on consolidated obligations designated under the fair value option are expensed as incurred in non-interest expense. Concessions paid on consolidated obligations not designated under the fair value option are deferred and amortized to expense using the level-yield method over the remaining contractual life or on a retrospective basis over the estimated life of the consolidated obligations. |
| Shares Subject to Mandatory Redemption, Changes in Redemption Value, Policy [Policy Text Block] | The Bank reclassifies the capital stock subject to redemption from capital to a liability after a member provides the Bank with a written notice of redemption; gives notice of intention to withdraw from membership; or attains nonmember status by merger or acquisition, charter termination, or other involuntary membership termination; or after a receiver or other liquidating agent for a member transfers the member's Bank capital stock to a nonmember entity, resulting in the member's shares then meeting the definition of a mandatorily redeemable financial instrument. Shares meeting this definition are reclassified to a liability at fair value. Dividends declared on shares classified as a liability are accrued at the expected dividend rate and reflected as interest expense in the Statements of Income. The repayment of these mandatorily redeemable financial instruments (by repurchase or redemption of the shares) is reflected as a financing cash outflow in the Statements of Cash Flows once settled. See Note 15 – Capital for more information. If a member cancels its written notice of redemption or notice of withdrawal or if the Bank allows the transfer of mandatorily redeemable capital stock to a member, the Bank reclassifies mandatorily redeemable capital stock from a liability to capital. After the reclassification, dividends on the capital stock are no longer classified as interest expense. |
| Regulator Expenses, Cost Assessed on Federal Home Loan Bank, Policy [Policy Text Block] | The FHLBanks fund a portion of the costs of operating the Finance Agency, and each FHLBank is assessed a proportionate share of those costs. The Finance Agency allocates its expenses and working capital fund among the FHLBanks based on the ratio between each FHLBank's minimum required regulatory capital and the aggregate minimum required regulatory capital of all the FHLBanks. |
| Office of Finance Cost Assessed on Federal Home Loan Bank, Policy [Policy Text Block] | Each FHLBank is assessed a proportionate share of the cost of operating the Office of Finance, which facilitates the issuance and servicing of consolidated obligations. The Office of Finance allocates its operating and capital expenditures among the FHLBanks as follows: (1) two-thirds of the assessment is based on each FHLBank's share of total consolidated obligations outstanding, and (2) one-third of the assessment is based on an equal pro rata allocation. |
| Federal Home Loan Bank Assessments, Policy [Policy Text Block] | As more fully discussed in Note 13 – Affordable Housing Program , the FHLBank Act requires each FHLBank to establish and fund an Affordable Housing Program (AHP). The Bank charges the required funding for the AHP to earnings and establishes a liability. The AHP funds provide subsidies to members to assist in the purchase, construction, or rehabilitation of housing for very low-, low-, and moderate-income households. Subsidies may be in the form of direct grants or below-market interest rate advances. The Bank accrues its AHP assessment monthly based on its net earnings. If the Bank experienced a net loss during a quarter but still had net earnings for the year, the Bank's obligation to the AHP would be calculated based on the Bank's year-to-date net earnings. If the Bank had net earnings in subsequent quarters, it would be required to contribute additional amounts to meet its calculated annual obligation. If the Bank experienced a net loss for a full year, the amount of the AHP liability would be equal to zero, since each FHLBank's required annual AHP contribution is limited to its annual net earnings. However, if the result of the aggregate 10% calculation is less than $100 for the FHLBanks combined, then the FHLBank Act requires that each FHLBank contribute such prorated sums as may be required to ensure that the aggregate contribution of the FHLBanks equals $100 . The proration would be made on the basis of an FHLBank's income in relation to the income of all the FHLBanks for the previous year. |
| Revenue Recognition Accounting Policy [Policy Text Block] | Letter of credit fees are recorded as other income over the term of the letter of credit. Litigation settlement gains, net of related legal expenses, are recorded in Other Income/(Loss) in “Gains on litigation settlements, net” in the Statements of Income. A litigation settlement gain is considered realized and recorded when the Bank receives cash or assets that are readily convertible to known amounts of cash or claims to cash. In addition, a litigation settlement gain is considered realizable and recorded when the Bank enters into a signed agreement that is not subject to appeal, where the counterparty has the ability to pay, and the amount to be received can be reasonably estimated. Prior to being realized or realizable, the Bank considers potential litigation settlement gains to be gain contingencies, and therefore they are not recorded in the Statements of Income. The related legal expenses are contingent-based fees and are only incurred and recorded upon a litigation settlement gain. |
| New Accounting Pronouncements, Policy [Policy Text Block] | Premium Amortization on Purchased Callable Debt Securities. On March 30, 2017, the FASB issued amended guidance to shorten the amortization period for certain purchased callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. This guidance affects all entities that hold investments in callable debt securities that have an amortized cost basis in excess of the amount that is repayable by the issuer at the earliest call date (that is, at a premium). This guidance is effective for the Bank for interim and annual periods beginning on January 1, 2019, and early adoption is permitted. This guidance should be applied using a modified retrospective method through a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The adoption of this guidance is not expected to have any effect on the Bank’s financial condition, results of operations, or cash flows. Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost. On March 10, 2017, the FASB issued amended guidance to improve the presentation of net periodic pension cost and net periodic postretirement benefit cost. The amendments require that employer disaggregate the service cost component from the other components of net benefit cost. The amendments also provide explicit guidance on how to present the service cost component and the other components of net benefit cost in the Statements of Income. This guidance became effective for the Bank for interim and annual periods beginning on January 1, 2018, and was adopted retrospectively for the presentation of the service cost component and the other components of net periodic pension cost and net periodic postretirement benefit cost in the Statements of Income. The adoption of this guidance did not have a material effect on the Bank’s financial condition, results of operations, cash flows, and financial statement disclosures. Classification of Certain Cash Receipts and Cash Payments. On August 26, 2016, the FASB issued amendments to clarify guidance on the classification of certain cash receipts and payments in the Statements of Cash Flows. This guidance is intended to reduce existing diversity in practice in how certain cash receipts and cash payments are presented and classified on the Statements of Cash Flows. This guidance became effective for the Bank for interim and annual periods beginning on January 1, 2018. The adoption of this guidance did not have any effect on the Bank’s financial condition, results of operations, or cash flows. Measurement of Credit Losses on Financial Instruments. On June 16, 2016, the FASB issued amended guidance for the accounting for credit losses on financial instruments. The amendments require entities to measure expected credit losses based on relevant information about past events, including historical experience, current conditions, and reasonable and supportable forecasts that affect the collectability of the reported amount. An entity must use judgment in determining the relevant information and estimation methods that are appropriate under the circumstances. In addition, under the new guidance, a financial asset, or a group of financial assets, is required to be measured at its amortized cost to be presented at the net amount expected to be collected over the contractual term of the financial assets. Among other things, the guidance also requires: • The Statement of Income to reflect the measurement of credit losses for newly recognized financial assets, as well as the expected increases or decreases of expected credit losses that have taken place during the period. • The entities to determine the allowance for credit losses for purchased financial assets with a more-than-insignificant amount of credit deterioration since origination that are measured at amortized cost basis in a similar manner to other financial assets measured at amortized cost basis. The initial allowance for credit losses is required to be added to the purchase price. • Credit losses relating to available-for-sale debt securities to be recorded through an allowance for credit losses. The amendments limit the allowance for credit losses to the amount by which fair value is below amortized cost. • Public entities to further disaggregate the current disclosure of credit quality indicators in relation to the amortized cost of financing receivables by the year of origination (i.e., vintage). The guidance is effective for the Bank for interim and annual periods beginning on January 1, 2020. Early application is permitted as of the interim and annual reporting periods beginning after December 15, 2018. The guidance should be applied using a modified-retrospective approach, through a cumulative-effect adjustment to retained earnings as of the beginning of the first reporting period in which the guidance is effective. In addition, the entities are required to use a prospective transition approach for purchased financial assets with a more-than-insignificant amount of credit deterioration since origination and for debt securities for which an other-than-temporary impairment had been recognized before the effective date. The Bank does not intend to adopt the guidance early. The Bank is in the process of evaluating this guidance and expects the adoption of the guidance may result in an increase in the allowance for credit losses given the requirement to assess losses for the entire estimated life of the financial asset, including an allowance for debt securities. The effect on the Bank’s financial condition, results of operations, and cash flows will depend on the composition of financial assets held by the Bank at the adoption date, as well as on economic conditions and forecasts at that time. Contingent Put and Call Options in Debt Instruments. On March 14, 2016, the FASB issued amendments to clarify the requirements for assessing whether contingent call (put) options that can accelerate the payment of principal on debt instruments are clearly and closely related to their debt hosts. The guidance requires entities to apply only the four-step decision sequence when assessing whether the economic characteristics and risks of call (put) options are clearly and closely related to the economic characteristics and risks of their debt hosts. Consequently, when a call (put) option is contingently exercisable, an entity does not have to assess whether the event that triggers the ability to exercise a call (put) option is related to interest rates or credit risks. This guidance became effective for the Bank for the interim and annual periods beginning on January 1, 2017. The adoption of this guidance had no effect on the Bank’s financial condition, results of operations, and cash flows. Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships. On March 10, 2016, the FASB issued amendments to clarify that a change in the counterparty to a derivative instrument that has been designated as the hedging instrument under U.S. GAAP does not, in and of itself, require dedesignation of that hedging relationship provided that all other hedge accounting criteria continue to be met. This guidance became effective for the Bank for the interim and annual periods beginning on January 1, 2017, and early adoption was permitted. The amendments provide entities with the option to apply the guidance using either a prospective approach or a modified retrospective approach, retrospectively applied to all derivative instruments that meet the specific conditions. The Bank elected to early adopt the guidance prospectively on January 1, 2016. The adoption of this guidance had no effect on the Bank’s financial condition, results of operations, and cash flows. Recognition of Lease Assets and Lease Liabilities. On February 25, 2016, the FASB issued guidance that requires recognition of lease assets and lease liabilities on the Statements of Condition and disclosure of key information about leasing arrangements. In particular, this guidance requires a lessee of operating or finance leases to recognize on the Statements of Condition a liability to make lease payments and a right-of-use asset representing its right to use the underlying asset for the lease term. However, for leases with a term of 12 months or less, a lessee is permitted to make an accounting policy election not to recognize lease assets and lease liabilities. Under previous U.S. GAAP, a lessee was not required to recognize lease assets and lease liabilities arising from operating leases on the Statements of Condition. While this guidance does not fundamentally change lessor accounting, some changes have been made to align that guidance with the lessee guidance and other areas within U.S. GAAP. The guidance becomes effective for the Bank for the interim and annual periods beginning on January 1, 2019, and early application is permitted. The guidance requires lessors and lessees to recognize and measure leases at the beginning of the earliest period presented in the financial statements using a modified retrospective approach. The Bank does not intend to adopt this guidance early. Upon adoption, the Bank expects to report higher assets and liabilities as a result of recording right-of-use assets and lease liabilities for its existing leases on the Statements of Condition. The Bank is in the process of evaluating this guidance, but its effect on the Bank’s financial condition, results of operations, and cash flows is not expected to be material. Recognition and Measurement of Financial Assets and Financial Liabilities. On January 5, 2016, the FASB issued amended guidance on certain aspects of recognition, measurement, presentation, and disclosure of financial instruments. This guidance includes, but is not limited to, the following: • Requires equity investments (with certain exceptions) to be measured at fair value with changes in fair value recognized in net income; • Requires an entity to present separately in other comprehensive income the portion of the total change in the fair value of a liability resulting from a change in the instrument-specific credit risk when the entity has elected to measure the liability at fair value in accordance with the fair value option for financial instruments; • Requires separate presentation of financial assets and financial liabilities by measurement category and form of financial asset on the Statement of Condition or in the accompanying notes to the financial statements; • Eliminates the requirement for public entities to disclose the method(s) and significant assumptions used to estimate the fair value that is required to be disclosed for financial instruments measured at amortized cost on the Statement of Condition. The guidance became effective for the Bank for the interim and annual periods beginning on January 1, 2018. The adoption of this guidance affected the Bank’s disclosures. However, the requirement to present the instrument-specific credit risk in other comprehensive income did not have any effect on the Bank’s financial condition, results of operations, and cash flows. Revenue from Contracts with Customers. On May 28, 2014, the FASB issued its guidance on revenue from contracts with customers. This guidance outlines a comprehensive model for recognizing revenue arising from contracts with customers and supersedes most current revenue recognition guidance. In addition, this guidance amends the existing requirements for the recognition of a gain or loss on the transfer of non-financial assets that are not in a contract with a customer. This guidance applies to all contracts with customers except those that are within the scope of certain other standards, such as financial instruments, certain guarantees, insurance contracts, and lease contracts. The guidance provides entities with the option of using either of the following adoption methods: a full retrospective method, applied retrospectively to each prior reporting period presented; or a modified retrospective method, with the cumulative effect of retrospectively applying this guidance recognized at the date of initial application. On August 12, 2015, the FASB issued an amendment to defer the effective date of the guidance issued in May 2014 by one year. In 2016 and 2017, the FASB issued additional amendments to clarify certain aspects of the new revenue guidance. However, the amendments do not change the core principle in the new revenue standard. The guidance became effective for the Bank for interim and annual periods beginning on January 1, 2018. Given that the majority of the Bank’s financial instruments and other contractual rights that generate revenue are covered by other accounting guidance under U.S. GAAP, the effect of this guidance on the Bank’s financial condition, results of operations, and cash flows was not material |
| Cash and Cash Equivalents, Policy [Policy Text Block] | Cash on hand, cash items in the process of collection, and amounts due from correspondent banks and the Federal Reserve Bank are included in Cash and due from banks on the Statements of Condition. Cash and due from banks includes certain compensating balances, where the Bank maintains collected cash balances with commercial banks in consideration for certain services. |
| Loans and Leases Receivable, Origination Fees, Discounts or Premiums, and Direct Costs to Acquire Loans Policy [Policy Text Block] | The participating financial institution and the Bank share the risk of credit losses on conventional MPF loan products by structuring potential losses on conventional MPF loans into layers with respect to each master commitment. After any primary mortgage insurance, the Bank is obligated to incur the first layer or portion of credit losses not absorbed by the liquidation value of the real property securing the loan. Under the MPF Program, the participating financial institution’s credit enhancement protection consists of the credit enhancement amount, which may be a direct obligation of the participating financial institution or may be a supplemental mortgage insurance policy paid for by the participating financial institution, and may include a contingent performance-based credit enhancement fee payable to the participating financial institution. The participating financial institution is required to pledge collateral to secure any portion of its credit enhancement amount that is a direct obligation. For taking on the credit enhancement obligation, the Bank pays the participating financial institution or any successor a credit enhancement fee, typically 10 basis points per annum, which is calculated on the remaining unpaid principal balance of the mortgage loans. A participating financial institution may elect to receive the credit enhancement fees monthly over the life of the loans or as an upfront lump sum amount that is included in the purchase price at the time loans are sold to the Bank. The lump sum amount is approximately equivalent to the present value of the monthly credit enhancement fees that the Bank would otherwise be expected to pay over the life of the loans. The Bank records credit enhancement fees as a reduction to interest income. |
| Derivatives, Methods of Accounting, Hedging Derivatives [Policy Text Block] | The Bank may use derivatives to adjust the repricing and options characteristics of advances to more closely match the characteristics of the Bank’s funding liabilities. In general, whenever a member executes a fixed or variable rate advance with embedded options, the Bank will simultaneously execute an interest rate exchange agreement with terms that offset the terms and embedded options in the advance. The combination of the advance and the interest rate exchange agreement effectively creates a variable rate asset. This type of hedge relationship receives fair value option accounting treatment. In addition, for certain advances for which the Bank has elected the fair value option, the Bank will simultaneously execute an interest rate exchange agreement with terms that economically offset the terms of the advance. However, this type of hedge is treated as an economic hedge because these combinations generally do not meet the requirements for fair value hedge accounting treatment. The Bank documents at inception all relationships between derivatives designated as hedging instruments and hedged items, its risk management objectives and strategies for undertaking various hedge transactions, and its method of assessing hedge effectiveness. Derivatives designated as fair value hedges may be transacted to hedge: (i) assets and liabilities on the Statement of Condition, (ii) firm commitments, or (iii) forecasted transactions. The Bank also formally assesses (both at hedge inception and on an ongoing basis) whether the hedging derivatives have been effective in offsetting changes in the fair value of hedged items attributable to the hedged risk and whether those derivatives may be expected to remain effective hedges in future periods. The Bank typically uses regression analyses or other statistical analyses to assess the effectiveness of its hedges. When it is determined that a derivative has not been or is not expected to be effective as a hedge, the Bank discontinues hedge accounting prospectively. The notional amount of an interest rate exchange agreement serves as a factor in determining periodic interest payments or cash flows received and paid. However, the notional amount of derivatives represents neither the actual amounts exchanged nor the overall exposure of the Bank to credit risk and market risk. The risks of derivatives can be measured meaningfully on a portfolio basis by taking into account the counterparties, the types of derivatives, the items being hedged, and any offsets between the derivatives and the items being hedged. The Bank may enter into interest rate swaps (including callable, putable, and basis swaps); and cap and floor agreements (collectively, interest rate exchange agreements or derivatives). Most of the Bank’s interest rate exchange agreements are executed in conjunction with the origination of advances or the issuance of consolidated obligation bonds to create variable rate structures. The interest rate exchange agreements are generally executed at the same time the advances and bonds are transacted and generally have the same maturity dates as the related advances and bonds. The Bank transacts most of its derivatives with large banks and major broker-dealers. Some of these banks and broker-dealers or their affiliates buy, sell, and distribute consolidated obligations. Over-the-counter derivatives may be either uncleared or cleared. In an uncleared derivative transaction, the Bank’s counterparty is the executing bank or broker-dealer. In a cleared derivative transaction, the Bank may execute the transaction either directly with the executing bank or broker-dealer or on a swap execution facility, but in either case, the Bank’s counterparty is a derivatives clearing organization or clearinghouse once the derivative transaction has been accepted for clearing. The Bank is not a derivatives dealer and does not trade derivatives for short-term profit. Additional uses of interest rate exchange agreements include: (i) offsetting embedded features in assets and liabilities, (ii) hedging anticipated issuance of debt, (iii) matching against consolidated obligation discount notes or bonds to create the equivalent of callable or non-callable fixed rate debt, (iv) modifying the repricing frequency of assets and liabilities, (v) matching against certain advances and consolidated obligations for which the Bank elected the fair value option, and (vi) exactly offsetting other derivatives cleared at a derivatives clearing organization. The Bank’s use of interest rate exchange agreements results in one of the following classifications: (i) a fair value hedge of an underlying financial instrument, (ii) an economic hedge of assets or liabilities, or (iii) an intermediary transaction for members. The Bank primarily uses the following derivative instruments: Interest Rate Swaps – An interest rate swap is an agreement between two entities to exchange cash flows in the future. The agreement sets the dates on which the cash flows will be paid and the manner in which the cash flows will be calculated. One of the simplest forms of an interest rate swap involves the promise by one party to pay cash flows equivalent to the interest on a notional principal amount at a predetermined fixed rate for a given period of time. In return for this promise, the party receives cash flows equivalent to the interest on the same notional principal amount at a variable rate for the same period of time. The variable rate received or paid by the Bank in most interest rate exchange agreements is either indexed to LIBOR or to the overnight index swap rate. Interest Rate Caps and Floors – In a cap agreement, additional cash flow is generated if the price or interest rate of an underlying variable rate rises above a certain threshold (or cap) price. In a floor agreement, additional cash flow is generated if the price or interest rate of an underlying variable rate falls below a certain threshold (or floor) price. Caps and floors may be used in conjunction with assets or liabilities. In general, caps and floors are designed as protection against the interest rate on a variable rate asset or liability rising above or falling below a certain level. The Bank may have the following types of hedged items: Investments – The Bank may invest in U.S. Treasury and agency obligations, agency MBS, and the taxable portion of highly rated state or local housing finance agency obligations. In the past, the Bank has also invested in PLRMBS rated AAA at the time of acquisition. The interest rate and prepayment risk associated with these investment securities is managed through a combination of debt issuance and derivatives. The Bank may manage prepayment risk and interest rate risk by funding investment securities with consolidated obligations that have call features or by hedging the prepayment risk with a combination of consolidated obligations and callable swaps. The Bank may execute callable swaps in conjunction with the issuance of certain liabilities to create funding that is economically equivalent to fixed rate callable debt. Although these derivatives are economic hedges against prepayment risk and are designated to individual liabilities, they do not receive either fair value or cash flow hedge accounting treatment. Investment securities may be classified as trading, AFS, or HTM. The Bank may also manage the risk arising from changing market prices or cash flows of investment securities classified as trading by entering into interest rate exchange agreements (economic hedges) that offset the changes in fair value or cash flows of the securities. The market value changes of both the trading securities and the associated interest rate exchange agreements are included in other income in the Statements of Income. Advances – The Bank offers a wide range of advances structures to meet members’ funding needs. These advances may have maturities up to 30 years with fixed or adjustable rates and may include early termination features or options. The Bank may use derivatives to adjust the repricing and options characteristics of advances to more closely match the characteristics of the Bank’s funding liabilities. In general, whenever a member executes a fixed or variable rate advance with embedded options, the Bank will simultaneously execute an interest rate exchange agreement with terms that offset the terms and embedded options in the advance. The combination of the advance and the interest rate exchange agreement effectively creates a variable rate asset. In addition, for certain advances for which the Bank has elected the fair value option, the Bank will simultaneously execute an interest rate exchange agreement with terms that economically offset the terms of the advance. Mortgage Loans – The Bank’s investment portfolio includes fixed rate mortgage loans. The prepayment options embedded in mortgage loans can result in extensions or contractions in the expected repayment of these investments, depending on changes in estimated prepayment speeds. The Bank manages the interest rate risk and prepayment risk associated with fixed rate mortgage loans through a combination of debt issuance and derivatives. The Bank uses both callable and non-callable debt to achieve cash flow patterns and market value sensitivities for liabilities similar to those expected on the mortgage loans. Net income could be reduced if the Bank replaces prepaid mortgage loans with lower-yielding assets and the Bank’s higher funding costs are not reduced accordingly. The Bank executes callable swaps in conjunction with the issuance of certain consolidated obligations to create funding that is economically equivalent to fixed rate callable bonds. Although these derivatives are economic hedges against the prepayment risk of specific loan pools and are referenced to individual liabilities, they do not receive either fair value or cash flow hedge accounting treatment. Consolidated Obligations – Consolidated obligation bonds may be structured to meet the Bank’s or the investors’ needs. Common structures include fixed rate bonds with or without call options and adjustable rate bonds with or without embedded options. In general, when bonds are issued, the Bank simultaneously executes an interest rate exchange agreement with terms that offset the terms and embedded options, if any, of the consolidated obligation bond. This combination of the consolidated obligation bond and the interest rate exchange agreement effectively creates an adjustable rate bond. The cost of this funding combination is generally lower than the cost that would be available through the issuance of an adjustable rate bond alone. These transactions generally receive fair value hedge accounting treatment. When the Bank issues consolidated obligation discount notes, it may also simultaneously enter into an interest rate exchange agreement to convert the fixed rate discount note to an adjustable rate discount note. This type of hedge is treated as an economic hedge. In addition, when certain consolidated obligation bonds for which the Bank has elected the fair value option are issued, the Bank simultaneously executes an interest rate exchange agreement with terms that economically offset the terms of the consolidated obligation bond. However, this type of hedge is treated as an economic hedge because these combinations do not meet the requirements for fair value hedge accounting treatment. Intermediation and Offsetting Derivatives – As an additional service to its members, the Bank has in the past entered into offsetting interest rate exchange agreements, acting as an intermediary between offsetting derivative transactions with members and other counterparties. This intermediation allows members indirect access to the derivatives market. The Bank also enters into derivatives to offset the economic effect of other derivatives that are no longer designated to advances, investments, or consolidated obligations. Neither type of offsetting derivatives receives hedge accounting treatment and both are separately marked to market through earnings. The net result of the accounting for these derivatives does not significantly affect the operating results of the Bank. |
| Loans and Leases Receivable, Troubled Debt Restructuring Policy [Policy Text Block] | Troubled debt restructuring (TDR) is considered to have occurred when a concession is granted to the debtor for economic or legal reasons related to the debtor’s financial difficulties and that concession would not have been considered otherwise. An MPF loan considered a TDR is individually evaluated for impairment when determining its related allowance for credit losses. Credit loss is measured by factoring in expected cash flow shortfalls incurred as of the reporting date as well as the economic loss attributable to delaying the original contractual principal and interest due dates, if applicable. |
| Derivatives, Embedded Derivatives [Policy Text Block] | The Bank did not have any bonds with embedded features that met the requirements to separate the embedded feature from the host contract and designate the embedded feature as a stand-alone derivative at December 31, 2017 or 2016 . The Bank has generally elected to account for certain bonds with embedded features under the fair value option, and these bonds are carried at fair value on the Statements of Condition. hen a callable bond for which the Bank is the primary obligor is issued, the Bank may simultaneously enter into an interest rate swap (in which the Bank pays a variable rate and receives a fixed rate) with a call feature that mirrors the call option embedded in the bond (a sold callable swap). |
| Stockholders' Equity, Policy [Policy Text Block] | Dividends on capital stock are recognized as dividends on the Statements of Capital Accounts, and dividends on mandatorily redeemable capital stock are recognized as interest expense on the Statements of Income. The Bank issues only one class of capital stock, Class B stock, with a par value of one hundred dollars per share, which may be redeemed (subject to certain conditions) upon five years' notice by the member to the Bank. In addition, at its discretion, under certain conditions, the Bank may repurchase excess capital stock at any time. (See “Excess Capital Stock” below for more information.) The capital stock may be issued, redeemed, and repurchased only at its stated par value, subject to certain statutory and regulatory requirements. The Bank may only redeem or repurchase capital stock from a shareholder if, following the redemption or repurchase, the shareholder will continue to meet its minimum capital stock requirement and the Bank will continue to meet its regulatory requirements for total capital, leverage capital, and risk-based capital. Under the Housing Act, the Director of the Finance Agency is responsible for setting the risk-based capital standards for the FHLBanks. The FHLBank Act and regulations governing the operations of the FHLBanks require that the Bank’s minimum capital stock requirement for shareholders must be sufficient to enable the Bank to meet its regulatory requirements for total capital, leverage capital, and risk-based capital. The Bank must maintain: (i) total regulatory capital in an amount equal to at least 4% of its total assets, (ii) leverage capital in an amount equal to at least 5% of its total assets, and (iii) permanent capital in an amount that is greater than or equal to its risk-based capital requirement. Because the Bank issues only Class B stock, regulatory capital and permanent capital for the Bank are both composed of retained earnings and Class B stock, including mandatorily redeemable capital stock (which is classified as a liability for financial reporting purposes). Regulatory capital and permanent capital do not include AOCI. Leverage capital is defined as the sum of permanent capital, weighted by a 1.5 multiplier, plus non-permanent capital. The risk-based capital requirement is equal to the sum of the Bank’s credit risk, market risk, and operations risk capital requirements, all of which are calculated in accordance with the rules and regulations of the Finance Agency. The Finance Agency may require an FHLBank to maintain a greater amount of permanent capital than is required by the risk-based capital requirement as defined. The Bank reclassifies the capital stock subject to redemption from capital to a liability after a member provides the Bank with a written notice of redemption; gives notice of intention to withdraw from membership; or attains nonmember status by merger or acquisition, charter termination, or other involuntary membership termination; or after a receiver or other liquidating agent for a member transfers the member's Bank capital stock to a nonmember entity, resulting in the member's shares then meeting the definition of a mandatorily redeemable financial instrument. Shares meeting this definition are reclassified to a liability at fair value. Dividends declared on shares classified as a liability are accrued at the expected dividend rate and reflected as interest expense in the Statements of Income. The repayment of these mandatorily redeemable financial instruments (by repurchase or redemption of the shares) is reflected as a financing cash outflow in the Statements of Cash Flows once settled. The Bank has a cooperative ownership structure under which members, former members, and certain other nonmembers own the Bank's capital stock. Former members and certain other nonmembers are required to maintain their investment in the Bank's capital stock until their outstanding transactions are paid off or until their capital stock is redeemed following the relevant five-year redemption period for capital stock or is repurchased by the Bank, in accordance with the Bank's capital requirements. Capital stock cannot be issued, repurchased, redeemed, or transferred except between the Bank and its members (or their affiliates and successors) at the capital stock's par value of one hundred dollars per share. If a member cancels its written notice of redemption or notice of withdrawal or if the Bank allows the transfer of mandatorily redeemable capital stock to a member, the Bank reclassifies mandatorily redeemable capital stock from a liability to capital. After the reclassification, dividends on the capital stock are no longer classified as interest expense. |
| Pension and Other Postretirement Plans, Policy [Policy Text Block] | Qualified Defined Benefit Plan. The Bank provides retirement benefits through a Bank-sponsored Cash Balance Plan, a qualified defined benefit plan. The Cash Balance Plan is provided to all employees who have completed six months of Bank service. Under the plan, each eligible Bank employee accrues benefits annually equal to 6% of the employee's annual compensation, plus 6% interest on the benefits accrued to the employee through the prior yearend. The Cash Balance Plan is funded through a qualified trust established by the Bank. Non-Qualified Defined Benefit Plans. The Bank sponsors the following non-qualified defined benefit retirement plans: • Benefit Equalization Plan, a non-qualified retirement plan restoring benefits offered under the Cash Balance Plan that are limited by laws governing the plan. See below for further discussion of the defined contribution portion of the Benefit Equalization Plan. • Supplemental Executive Retirement Plan (SERP), a non-qualified unfunded retirement benefit plan available to the Bank's eligible senior officers, which generally provides a service-linked supplemental cash balance annual contribution credit to SERP participants and an annual interest credit of 6% on the benefits accrued to the SERP participants through the prior yearend. • Deferred Compensation Plan, a non-qualified retirement plan available to all eligible Bank officers, which provides make-up pension benefits that would have been earned under the Cash Balance Plan had the compensation not been deferred. The make-up benefits vest according to the corresponding provisions of the Cash Balance Plan. See below for further discussion of the defined contribution portion of the Deferred Compensation Plan. Postretirement Health Benefit Plan. The Bank provides a postretirement health benefit plan to employees hired before January 1, 2003. The Bank's costs are capped at 1998 health care premium amounts. As a result, changes in health care cost trend rates will have no effect on the Bank's accumulated postretirement benefit obligation or service and interest costs. Retirement Savings Plan. The Bank sponsors a qualified defined contribution retirement 401(k) savings plan, the Federal Home Loan Bank of San Francisco Savings Plan (Savings Plan). Contributions to the Savings Plan consist of elective participant contributions of up to 20% of each participant's base compensation and a Bank matching contribution of up to 6% of each participant's base compensation. The Bank uses a discount rate to determine the present value of its future benefit obligations. The discount rate was determined based on the Citigroup Pension Discount Curve at the measurement date. The Citigroup Pension Discount Curve is a yield curve that reflects the market-observed yields for high-quality fixed income securities for each maturity. The projected benefit payments for each year from the plan are discounted using the spot rates on the yield curve to derive a single equivalent discount rate. The discount rate is reset annually on the measurement date. The expected return on plan assets was determined based on: (i) the historical returns for each asset class, (ii) the expected future long-term returns for these asset classes, and (iii) the plan's target asset allocation. The Cash Balance Plan is administered by the Bank's Retirement Committee, which establishes the plan's Statement of Investment Policy and Objectives. The Retirement Committee has adopted a strategic asset allocation based on a stable distribution of assets among major asset classes. These asset classes include domestic large-, mid-, and small-capitalization equity investments; international equity investments; real return investments; and fixed income investments. The Retirement Committee has set the Cash Balance Plan's target allocation percentages for a mix of 60% equity, 10% real return, and 30% fixed income. The Retirement Committee reviews the performance of the Cash Balance Plan on a regular basis. Deferred Compensation Plan. The Bank maintains a deferred compensation plan that is available to all eligible Bank officers. The defined contribution portion of the plan is comprised of two components: (i) officer or director deferral of current compensation, and (ii) make-up matching contributions for officers that would have been made by the Bank under the Savings Plan had the compensation not been deferred. The make-up benefits under the Deferred Compensation Plan vest according to the corresponding provisions of the Savings Plan. The Deferred Compensation Plan liability consists of the accumulated compensation deferrals and accrued earnings on the deferrals, as well as the make-up matching contributions and any accrued earnings on the contributions. Benefit Equalization Plan. The Bank sponsors a non-qualified retirement plan restoring benefits offered under the Savings Plan that have been limited by laws governing the plan. |
| Segment Reporting, Policy [Policy Text Block] | The Bank uses an analysis of financial results based on the financial components and adjusted net interest income of two operating segments, the advances-related business and the mortgage-related business, as well as other financial information, to review and assess financial performance and determine financial management strategies related to the operations of these two business segments. For purposes of segment reporting, adjusted net interest income includes income and expense associated with net settlements from economic hedges that are recorded in “Net gain/(loss) on derivatives and hedging activities” in other income and excludes interest expense that is recorded in “Mandatorily redeemable capital stock.” Other key financial information, such as any credit-related OTTI losses on the Bank’s PLRMBS, other expenses, and assessments, is not included in the segment reporting analysis, but is incorporated into the Bank’s overall assessment of financial performance. The advances-related business consists of advances and other credit products, related financing and hedging instruments, other non-MBS investments associated with the Bank's role as a liquidity provider, and capital. Adjusted net interest income for this segment is derived primarily from the difference, or spread, between the yield on all assets associated with the business activities in this segment and the cost of funding those activities, including the net settlements from associated interest rate exchange agreements, and from earnings on invested capital. The mortgage-related business consists of MBS investments, mortgage loans acquired through the MPF Program, the consolidated obligations specifically identified as funding those assets, and related hedging instruments. Adjusted net interest income for this segment is derived primarily from the difference, or spread, between the yield on the MBS and mortgage loans and the cost of the consolidated obligations funding those assets. This includes the net settlements from associated interest rate exchange agreements and net accretion related income, which is a result of improvement in expected cash flows on certain other-than-temporarily-impaired PLRMBS, less the provision for credit losses on mortgage loans. |
| Derivatives, Hedge Discontinuances [Policy Text Block] | The Bank discontinues hedge accounting prospectively when: (i) it determines that the derivative is no longer effective in offsetting changes in the fair value of a hedged item (including hedged items such as firm commitments or forecasted transactions); (ii) the derivative and/or the hedged item expires or is sold, terminated, or exercised; (iii) it is no longer probable that the forecasted transaction will occur in the originally expected period; (iv) a hedged firm commitment no longer meets the definition of a firm commitment; (v) it determines that designating the derivative as a hedging instrument is no longer appropriate; or (vi) it decides to use the derivative to offset changes in the fair value of other derivatives or instruments carried at fair value. |
| Fair Value of Financial Instruments, Policy [Policy Text Block] | The fair value option provides an entity with an irrevocable option to elect fair value as an alternative measurement for selected financial assets, financial liabilities, unrecognized firm commitments, and written loan commitments not previously carried at fair value. It requires an entity to display the fair value of those assets and liabilities for which the entity has chosen to use fair value on the face of the Statements of Condition. Fair value is used for both the initial and subsequent measurement of the designated assets, liabilities, and commitments, with the changes in fair value recognized in net income. Interest income and interest expense on advances and consolidated bonds carried at fair value are recognized solely on the contractual amount of interest due or unpaid. Any transaction fees or costs are immediately recognized in non-interest income or non-interest expense. The Bank elected the fair value option for certain financial instruments as follows: • Adjustable rate advances with embedded options (excluding call and put options) • Callable fixed rate advances • Putable fixed rate advances • Putable fixed rate advances with embedded options • Fixed rate advances with partial prepayment symmetry • Callable or non-callable capped floater consolidated obligation bonds • Convertible consolidated obligation bonds • Adjustable or fixed rate range accrual consolidated obligation bonds • Ratchet consolidated obligation bonds • Adjustable rate advances indexed to non-LIBOR indices such as the Prime Rate, U.S. Treasury bill, and Federal funds effective rate • Adjustable rate consolidated obligation bonds indexed to non-LIBOR indices such as the Prime Rate and U.S. Treasury bill • Step-up callable bonds, which pay interest at increasing fixed rates for specified intervals over the life of the bond and can generally be called at the Bank's option on the step-up dates • Step-down callable bonds, which pay interest at decreasing fixed rates for specified intervals over the life of the bond and can generally be called at the Bank's option on the step-down dates The Bank has elected the fair value option for certain financial instruments to assist in mitigating potential earnings volatility that can arise from economic hedging relationships in which the carrying value of the hedged item is not adjusted for changes in fair value. The potential earnings volatility associated with using fair value only for the derivative is the Bank’s primary reason for electing the fair value option for financial assets and liabilities that do not qualify for hedge accounting or that have not previously met or may be at risk for not meeting the hedge effectiveness requirements. Cash and Due from Banks – The estimated fair value equals the carrying value. Federal Funds Sold and Securities Purchased Under Agreements to Resell – The estimated fair value of overnight Federal funds sold and securities purchased under agreements to resell approximates the carrying value. The estimated fair value of term Federal funds sold and term securities purchased under agreements to resell has been determined by calculating the present value of expected cash flows for the instruments and reducing the amount for accrued interest receivable. The discount rates used in these calculations are the replacement rates for comparable instruments with similar terms. Interest-Bearing Deposits – The fair value of deposits is generally equal to the carrying value of the deposits because the deposits are primarily overnight deposits or due on demand. The Bank determines the fair values of term deposits by calculating the present value of expected future cash flows from the deposits and reducing the amount for accrued interest receivable. The discount rates used in these calculations are the cost of deposits with similar terms. Investment Securities – MBS – To value its MBS, the Bank obtains prices from multiple designated third-party pricing vendors when available. The pricing vendors use various proprietary models to price these securities. The inputs to those models are derived from various sources including, but not limited to: benchmark yields, reported trades, dealer estimates, issuer spreads, prices on benchmark securities, bids, offers, and other market-related data. Since many securities do not trade on a daily basis, the pricing vendors use available information as applicable, such as benchmark yield curves, benchmarking of like securities, sector groupings, and matrix pricing, to determine the prices for individual securities. Each pricing vendor has an established challenge process in place for all security valuations, which facilitates resolution of price discrepancies identified by the Bank. At least annually, the Bank conducts reviews of the multiple pricing vendors to update and confirm its understanding of the vendors’ pricing processes, methodologies, and control procedures. The Bank’s valuation technique for estimating the fair values of its MBS first requires the establishment of a median vendor price for each security. If three prices are received, the middle price is the median price; if two prices are received, the average of the two prices is the median price; and if one price is received, it is the median price (and also the default fair value) subject to additional validation. All vendor prices that are within a specified tolerance threshold of the median price are included in the cluster of vendor prices that are averaged to establish a default fair value. All vendor prices that are outside the threshold (outliers) are subject to further analysis including, but not limited to, comparison to prices provided by an additional third-party valuation service, prices for similar securities and/or dealer estimates, or use of internal model prices, which are deemed to be reflective of all relevant facts and circumstances that a market participant would consider. Such analysis is also applied in those limited instances where no third-party vendor price or only one third-party vendor price is available in order to arrive at an estimated fair value. If an outlier (or some other price identified in the analysis) is determined to be a better estimate of fair value, then the outlier (or the other price, as appropriate) is used as the fair value rather than the default fair value. If, instead, the analysis confirms that an outlier is (or outliers are) not representative of fair value and the default fair value is the best estimate, then the default fair value is used as the fair value. If all vendor prices received for a security are outside the tolerance threshold level of the median price, then there is no default fair value, and the fair value is determined by an evaluation of all outlier prices (or the other prices, as appropriate) as described above. As of December 31, 2017 , multiple vendor prices were received for most of the Bank’s MBS, and the fair value estimates for most of those securities were determined in accordance with the Bank’s valuation technique based on these vendor prices. Based on the Bank’s reviews of the pricing methods employed by the third-party pricing vendors and the relative lack of dispersion among the vendor prices (or, in those instances in which there were outliers, the Bank’s additional analyses), the Bank believes that its fair value estimates are reasonable and that the fair value measurements are classified appropriately in the fair value hierarchy. Based on limited market liquidity for PLRMBS, the fair value measurements for these securities were classified as Level 3 within the fair value hierarchy. Investment Securities – FFCB Bonds and CalHFA Bonds – The Bank estimates the fair values of these securities using the methodology described above for Investment Securities – MBS . Advances – Because quoted prices are not available for advances, the fair values are measured using model-based valuation techniques (such as calculating the present value of future cash flows and reducing the amount for accrued interest receivable). The Bank’s primary inputs for measuring the fair value of advances are market-based consolidated obligation yield curve (CO Curve) inputs obtained from the Office of Finance. The CO Curve is then adjusted to reflect the rates on replacement advances with similar terms and collateral. These spread adjustments are not market-observable and are evaluated for significance in the overall fair value measurement and the fair value hierarchy level of the advance. The Bank obtains market-observable inputs for complex advances. These inputs may include volatility assumptions, which are market-based expectations of future interest rate volatility implied from current market prices for similar options (swaption volatility and volatility skew). The discount rates used in these calculations are the replacement advance rates for advances with similar terms. Pursuant to the Finance Agency’s advances regulation, advances with an original term to maturity or repricing period greater than six months generally require a prepayment fee sufficient to make the Bank financially indifferent to the borrower’s decision to prepay the advances. The Bank determined that no adjustment is required to the fair value measurement of advances for prepayment fees. In addition, the Bank did not adjust its fair value measurement of advances for creditworthiness primarily because advances were fully collateralized. Mortgage Loans Held for Portfolio – The estimated fair value for seasoned mortgage loans represents modeled prices based on observable market prices for seasoned agency mortgage-backed passthrough securities adjusted for differences in coupon, average loan rate, credit, and cash flow remittance between the Bank’s mortgage loans and the referenced instruments, while the estimated fair value for newly originated mortgage loans represents modeled prices based on MPF commitment rates. Market prices are highly dependent on the underlying prepayment assumptions. Changes in the prepayment speeds often have a material effect on the fair value estimates. These underlying prepayment assumptions are susceptible to material changes in the near term because they are made at a specific point in time. Loans to and from Other FHLBanks – Because these are overnight transactions, the estimated fair value approximates the recorded carrying value. Accrued Interest Receivable and Payable – The estimated fair value approximates the carrying value of accrued interest receivable and accrued interest payable. Other Assets – The estimated fair value of grantor trust assets is based on quoted market prices. Derivative Assets and Liabilities – In general, derivative instruments transacted and held by the Bank for risk management activities are traded in over-the-counter markets where quoted market prices are not readily available. These derivatives are interest rate-related. For these derivatives, the Bank measures fair value using internally developed discounted cash flow models that use market-observable inputs, such as the overnight index swap (OIS) curve and volatility assumptions, which are market-based expectations of future interest rate volatility implied from current market prices for similar options (swaption volatility and volatility skew), adjusted for counterparty credit risk, as necessary. The Bank is subject to credit risk because of the risk of potential nonperformance by its derivative counterparties. To mitigate this risk, the Bank executes uncleared derivative transactions only with highly rated derivative dealers and major banks (derivative dealer counterparties) that meet the Bank’s eligibility criteria. In addition, the Bank has entered into master netting agreements and bilateral credit support agreements with all active derivative dealer counterparties that provide for delivery of collateral at specified levels to limit the Bank’s net unsecured credit exposure to these counterparties. Under these policies and agreements, the amount of unsecured credit exposure to an individual derivative dealer counterparty is either (i) limited to an absolute dollar credit exposure limit according to the counterparty’s long-term debt or deposit credit rating, as determined by rating agencies or (ii) set at zero (subject to a minimum transfer amount). The Bank clears its cleared derivative transactions only through clearing agents that meet the Bank’s eligibility requirements, and the Bank’s credit exposure to the clearinghouse is secured by variation margin received from the clearinghouse. All credit exposure from derivative transactions entered into by the Bank with member counterparties that are not derivative dealers must be fully secured by eligible collateral. The Bank evaluated the potential for the fair value of the instruments to be affected by counterparty credit risk and determined that no adjustments to the overall fair value measurements were required. The fair values of the derivative assets and liabilities include accrued interest receivable/payable and cash collateral remitted to/received from counterparties. The estimated fair values of the accrued interest receivable/payable and cash collateral approximate their carrying values because of their short-term nature. The fair values of derivatives that met the netting requirements are presented on a net basis. If these netted amounts are positive, they are classified as an asset and, if negative, they are classified as a liability. Deposits – The fair value of deposits is generally equal to the carrying value of the deposits because the deposits are primarily overnight deposits or due on demand. The Bank determines the fair values of term deposits by calculating the present value of expected future cash flows from the deposits and reducing the amount for accrued interest payable. The discount rates used in these calculations are the cost of deposits with similar terms. Consolidated Obligations – Because quoted prices in active markets are not generally available for identical liabilities, the Bank measures fair values using internally developed models that use primarily market-observable inputs. The Bank’s primary input for measuring the fair value of consolidated obligation bonds is a market-based CO Curve obtained from the Office of Finance. The Office of Finance constructs the CO Curve using the Treasury yield curve as a base curve, which is adjusted by indicative consolidated obligation spreads obtained from market-observable sources. These market indications are generally derived from pricing indications from dealers, historical pricing relationships, and market activity for similar liabilities, such as recent GSE issuances or secondary market activity. For consolidated obligation bonds with embedded options, the Bank also obtains market-observable inputs, such as volatility assumptions, which are market-based expectations of future interest rate volatility implied from current market prices for similar options (swaption volatility and volatility skew). Adjustments may be necessary to reflect the Bank’s credit quality or the credit quality of the FHLBank System when valuing consolidated obligation bonds measured at fair value. The Bank monitors its own creditworthiness and the creditworthiness of the other FHLBanks and the FHLBank System to determine whether any adjustments are necessary for creditworthiness in its fair value measurement of consolidated obligation bonds. The credit ratings of the FHLBank System and any changes to the credit ratings are the basis for the Bank to determine whether the fair values of consolidated obligations have been significantly affected during the reporting period by changes in the instrument-specific credit risk. Mandatorily Redeemable Capital Stock – The estimated fair value of capital stock subject to mandatory redemption is generally at par value as indicated by contemporaneous purchases, redemptions, and repurchases at par value. Fair value includes estimated dividends earned at the time of reclassification from capital to liabilities, until such amount is paid, and any subsequently declared capital stock dividend. The Bank’s capital stock can only be acquired by members at par value and redeemed or repurchased at par value, subject to statutory and regulatory requirements. The Bank’s capital stock is not traded, and no market mechanism exists for the exchange of Bank capital stock outside the cooperative ownership structure. Commitments – The estimated fair value of standby letters of credit is based on the present value of fees currently charged for similar agreements and is recorded in other liabilities. The estimated fair value of off-balance sheet fixed rate commitments to fund advances and commitments to issue consolidated obligations takes into account the difference between current and committed interest rates. The fair value hierarchy is used to prioritize the fair value methodologies and valuation techniques as well as the inputs to the valuation techniques used to measure fair value for assets and liabilities carried at fair value on the Statements of Condition. The inputs are evaluated and an overall level for the fair value measurement is determined. This overall level is an indication of market observability of the fair value measurement for the asset or liability. The fair value hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). An entity must disclose the level within the fair value hierarchy in which the measurements are classified for all financial assets and liabilities measured on a recurring or non-recurring basis. The application of the fair value hierarchy to the Bank’s financial assets and financial liabilities that are carried at fair value either on a recurring or non-recurring basis is as follows: • Level 1 – Quoted prices (unadjusted) for identical assets or liabilities in an active market that the reporting entity can access on the measurement date. • Level 2 – Inputs other than quoted prices within Level 1 that are observable inputs for the asset or liability, either directly or indirectly. If the asset or liability has a specified (contractual) term, a Level 2 input must be observable for substantially the full term of the asset or liability. Level 2 inputs include the following: (1) quoted prices for similar assets or liabilities in active markets; (2) quoted prices for identical or similar assets or liabilities in markets that are not active; (3) inputs other than quoted prices that are observable for the asset or liability (e.g., interest rates and yield curves that are observable at commonly quoted intervals, and implied volatilities); and (4) inputs that are derived principally from or corroborated by observable market data by correlation or other means. • Level 3 – Unobservable inputs for the asset or liability. A financial instrument’s categorization within the valuation hierarchy is based on the lowest level of input that is significant to the fair value measurement. The following assets and liabilities, including those for which the Bank has elected the fair value option, are carried at fair value on the Statements of Condition as of December 31, 2017 : • Trading securities • AFS securities • Certain advances • Derivative assets and liabilities • Certain consolidated obligation bonds • Certain other assets For instruments for which the fair value option has been elected, the related contractual interest income and contractual interest expense are recorded as part of net interest income on the Statements of Income. The remaining changes in fair value for instruments for which the fair value option has been elected are recorded as net gains/ (losses) on financial instruments held under the fair value option in the Statements of Income. The change in fair value does not include changes in instrument-specific credit risk. |
| Fair Value Transfer, Policy [Policy Text Block] | For instruments carried at fair value, the Bank reviews the fair value hierarchy classifications on a quarterly basis. Changes in the observability of the valuation inputs may result in a reclassification of certain assets or liabilities. Such reclassifications are reported as transfers in or out as of the beginning of the quarter in which the changes occur. For the periods presented, the Bank did not have any reclassifications for transfers in or out of the fair value hierarchy levels. |
| Commitments and Contingencies, Policy [Policy Text Block] | Delivery commitments are recorded at fair value as derivative assets or derivative liabilities in the Statements of Condition. |
