jpmorgan chase & co./2018 form 10-k 117 lending-related commitments the firm uses lending-related financial instruments , such as commitments ( including revolving credit facilities ) and guarantees , to address the financing needs of its clients . the contractual amounts of these financial instruments represent the maximum possible credit risk should the clients draw down on these commitments or the firm fulfill its obligations under these guarantees , and the clients subsequently fail to perform according to the terms of these contracts . most of these commitments and guarantees are refinanced , extended , cancelled , or expire without being drawn upon or a default occurring . in the firm 2019s view , the total contractual amount of these wholesale lending-related commitments is not representative of the firm 2019s expected future credit exposure or funding requirements . for further information on wholesale lending-related commitments , refer to note 27 . clearing services the firm provides clearing services for clients entering into certain securities and derivative contracts . through the provision of these services the firm is exposed to the risk of non-performance by its clients and may be required to share in losses incurred by ccps . where possible , the firm seeks to mitigate its credit risk to its clients through the collection of adequate margin at inception and throughout the life of the transactions and can also cease provision of clearing services if clients do not adhere to their obligations under the clearing agreement . for further discussion of clearing services , refer to note 27 . derivative contracts derivatives enable clients and counterparties to manage risks including credit risk and risks arising from fluctuations in interest rates , foreign exchange , equities , and commodities . the firm makes markets in derivatives in order to meet these needs and uses derivatives to manage certain risks associated with net open risk positions from its market-making activities , including the counterparty credit risk arising from derivative receivables . the firm also uses derivative instruments to manage its own credit and other market risk exposure . the nature of the counterparty and the settlement mechanism of the derivative affect the credit risk to which the firm is exposed . for otc derivatives the firm is exposed to the credit risk of the derivative counterparty . for exchange-traded derivatives ( 201cetd 201d ) , such as futures and options , and 201ccleared 201d over-the-counter ( 201cotc-cleared 201d ) derivatives , the firm is generally exposed to the credit risk of the relevant ccp . where possible , the firm seeks to mitigate its credit risk exposures arising from derivative contracts through the use of legally enforceable master netting arrangements and collateral agreements . for a further discussion of derivative contracts , counterparties and settlement types , refer to note 5 . the following table summarizes the net derivative receivables for the periods presented . derivative receivables .
what is the amount of the decrease observed in the total net of cash collateral during 2017 and 2018 , in millions of dollars?
( a ) includes collateral related to derivative instruments where appropriate legal opinions have not been either sought or obtained with respect to master netting agreements . the fair value of derivative receivables reported on the consolidated balance sheets were $ 54.2 billion and $ 56.5 billion at december 31 , 2018 and 2017 , respectively . derivative receivables represent the fair value of the derivative contracts after giving effect to legally enforceable master netting agreements and cash collateral held by the firm . however , in management 2019s view , the appropriate measure of current credit risk should also take into consideration additional liquid securities ( primarily u.s . government and agency securities and other group of seven nations ( 201cg7 201d ) government securities ) and other cash collateral held by the firm aggregating $ 15.3 billion and $ 16.1 billion at december 31 , 2018 and 2017 , respectively , that may be used as security when the fair value of the client 2019s exposure is in the firm 2019s favor . in addition to the collateral described in the preceding paragraph , the firm also holds additional collateral ( primarily cash , g7 government securities , other liquid government-agency and guaranteed securities , and corporate debt and equity securities ) delivered by clients at the initiation of transactions , as well as collateral related to contracts that have a non-daily call frequency and collateral that the firm has agreed to return but has not yet settled as of the reporting date . although this collateral does not reduce the balances and is not included in the table above , it is available as security against potential exposure that could arise should the fair value of the client 2019s derivative contracts move in the firm 2019s favor . the derivative receivables fair value , net of all collateral , also does not include other credit enhancements , such as letters of credit . for additional information on the firm 2019s use of collateral agreements , refer to note 5 . while useful as a current view of credit exposure , the net fair value of the derivative receivables does not capture the potential future variability of that credit exposure . to capture the potential future variability of credit exposure , the firm calculates , on a client-by-client basis , three measures of potential derivatives-related credit loss : peak , derivative risk equivalent ( 201cdre 201d ) , and average exposure ( 201cavg 201d ) . these measures all incorporate netting and collateral benefits , where applicable . peak represents a conservative measure of potential exposure to a counterparty calculated in a manner that is broadly equivalent to a 97.5% ( 97.5 % ) confidence level over the life of the transaction . peak is the primary measure used by the firm for setting of credit limits for derivative contracts , senior management reporting and derivatives exposure management . dre exposure is a measure that expresses the risk of derivative exposure on a basis intended to be .