credit commitments and lines of credit the table below summarizes citigroup 2019s credit commitments : in millions of dollars u.s . outside of u.s . december 31 , december 31 .
what percentage of total credit commitments as of december 31 , 2017 are credit card lines?
the majority of unused commitments are contingent upon customers maintaining specific credit standards . commercial commitments generally have floating interest rates and fixed expiration dates and may require payment of fees . such fees ( net of certain direct costs ) are deferred and , upon exercise of the commitment , amortized over the life of the loan or , if exercise is deemed remote , amortized over the commitment period . commercial and similar letters of credit a commercial letter of credit is an instrument by which citigroup substitutes its credit for that of a customer to enable the customer to finance the purchase of goods or to incur other commitments . citigroup issues a letter on behalf of its client to a supplier and agrees to pay the supplier upon presentation of documentary evidence that the supplier has performed in accordance with the terms of the letter of credit . when a letter of credit is drawn , the customer is then required to reimburse citigroup . one- to four-family residential mortgages a one- to four-family residential mortgage commitment is a written confirmation from citigroup to a seller of a property that the bank will advance the specified sums enabling the buyer to complete the purchase . revolving open-end loans secured by one- to four-family residential properties revolving open-end loans secured by one- to four-family residential properties are essentially home equity lines of credit . a home equity line of credit is a loan secured by a primary residence or second home to the extent of the excess of fair market value over the debt outstanding for the first mortgage . commercial real estate , construction and land development commercial real estate , construction and land development include unused portions of commitments to extend credit for the purpose of financing commercial and multifamily residential properties as well as land development projects . both secured-by-real-estate and unsecured commitments are included in this line , as well as undistributed loan proceeds , where there is an obligation to advance for construction progress payments . however , this line only includes those extensions of credit that , once funded , will be classified as total loans , net on the consolidated balance sheet . credit card lines citigroup provides credit to customers by issuing credit cards . the credit card lines are cancelable by providing notice to the cardholder or without such notice as permitted by local law . commercial and other consumer loan commitments commercial and other consumer loan commitments include overdraft and liquidity facilities as well as commercial commitments to make or purchase loans , purchase third-party receivables , provide note issuance or revolving underwriting facilities and invest in the form of equity . other commitments and contingencies other commitments and contingencies include committed or unsettled regular-way reverse repurchase agreements and all other transactions related to commitments and contingencies not reported on the lines above . unsettled reverse repurchase and securities lending agreements and unsettled repurchase and securities borrowing agreements in addition , in the normal course of business , citigroup enters into reverse repurchase and securities borrowing agreements , as well as repurchase and securities lending agreements , which settle at a future date . at december 31 , 2018 , and 2017 , citigroup had $ 36.1 billion and $ 35.0 billion unsettled reverse repurchase and securities borrowing agreements , respectively , and $ 30.7 billion and $ 19.1 billion unsettled repurchase and securities lending agreements , respectively . for a further discussion of securities purchased under agreements to resell and securities borrowed , and securities sold under agreements to repurchase and securities loaned , including the company 2019s policy for offsetting repurchase and reverse repurchase agreements , see note 11 to the consolidated financial statements. .