management 2019s discussion and analysis of financial condition and results of operations state street corporation | 89 $ 65.35 billion and $ 87.20 billion as of december 31 , 2017 and december 31 , 2016 , respectively . table 29 : components of average hqla by type of ( in millions ) december 31 , december 31 .
what percent of total balance is the excess central bank balances in 2017?
with respect to highly liquid short-term investments presented in the preceding table , due to the continued elevated level of client deposits as of december 31 , 2017 , we maintained cash balances in excess of regulatory requirements governing deposits with the federal reserve of approximately $ 33.58 billion at the federal reserve , the ecb and other non-u.s . central banks , compared to $ 48.40 billion as of december 31 , 2016 . the lower levels of deposits with central banks as of december 31 , 2017 compared to december 31 , 2016 was due to normal deposit volatility . liquid securities carried in our asset liquidity include securities pledged without corresponding advances from the frbb , the fhlb , and other non- u.s . central banks . state street bank is a member of the fhlb . this membership allows for advances of liquidity in varying terms against high-quality collateral , which helps facilitate asset-and-liability management . access to primary , intra-day and contingent liquidity provided by these utilities is an important source of contingent liquidity with utilization subject to underlying conditions . as of december 31 , 2017 and december 31 , 2016 , we had no outstanding primary credit borrowings from the frbb discount window or any other central bank facility , and as of the same dates , no fhlb advances were outstanding . in addition to the securities included in our asset liquidity , we have significant amounts of other unencumbered investment securities . the aggregate fair value of those securities was $ 66.10 billion as of december 31 , 2017 , compared to $ 54.40 billion as of december 31 , 2016 . these securities are available sources of liquidity , although not as rapidly deployed as those included in our asset liquidity . measures of liquidity include lcr , nsfr and tlac which are described in "supervision and regulation" included under item 1 , business , of this form 10-k . uses of liquidity significant uses of our liquidity could result from the following : withdrawals of client deposits ; draw- downs of unfunded commitments to extend credit or to purchase securities , generally provided through lines of credit ; and short-duration advance facilities . such circumstances would generally arise under stress conditions including deterioration in credit ratings . a recurring significant use of our liquidity involves our deployment of hqla from our investment portfolio to post collateral to financial institutions and participants in our agency lending program serving as sources of securities under our enhanced custody program . we had unfunded commitments to extend credit with gross contractual amounts totaling $ 26.49 billion and $ 26.99 billion as of december 31 , 2017 and december 31 , 2016 , respectively . these amounts do not reflect the value of any collateral . as of december 31 , 2017 , approximately 72% ( 72 % ) of our unfunded commitments to extend credit expire within one year . since many of our commitments are expected to expire or renew without being drawn upon , the gross contractual amounts do not necessarily represent our future cash requirements . information about our resolution planning and the impact actions under our resolution plans could have on our liquidity is provided in "supervision and regulation" included under item 1 . business , of this form 10-k . funding deposits we provide products and services including custody , accounting , administration , daily pricing , foreign exchange services , cash management , financial asset management , securities finance and investment advisory services . as a provider of these products and services , we generate client deposits , which have generally provided a stable , low-cost source of funds . as a global custodian , clients place deposits with state street entities in various currencies . as of december 31 , 2017 and december 31 , 2016 , approximately 60% ( 60 % ) of our average client deposit balances were denominated in u.s . dollars , approximately 20% ( 20 % ) in eur , 10% ( 10 % ) in gbp and 10% ( 10 % ) in all other currencies . for the past several years , we have frequently experienced higher client deposit inflows toward the end of each fiscal quarter or the end of the fiscal year . as a result , we believe average client deposit balances are more reflective of ongoing funding than period-end balances. .