pre_text: asset category target allocation total quoted prices in active markets for identical assets ( level 1 ) significant observable inputs ( level 2 ) significant unobservable inputs .
post_text: balance as of january 1 , 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 140 actual return on assets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 purchases , issuances and settlements , net . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136 balance as of december 31 , 2017 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . $ 278 the company 2019s postretirement benefit plans have different levels of funded status and the assets are held under various trusts . the investments and risk mitigation strategies for the plans are tailored specifically for each trust . in setting new strategic asset mixes , consideration is given to the likelihood that the selected asset allocation will effectively fund the projected plan liabilities and meet the risk tolerance criteria of the company . the company periodically updates the long-term , strategic asset allocations for these plans through asset liability studies and uses various analytics to determine the optimal asset allocation . considerations include plan liability characteristics , liquidity needs , funding requirements , expected rates of return and the distribution of returns . in 2012 , the company implemented a de-risking strategy for the american water pension plan after conducting an asset-liability study to reduce the volatility of the funded status of the plan . as part of the de-risking strategy , the company revised the asset allocations to increase the matching characteristics of fixed- income assets relative to liabilities . the fixed income portion of the portfolio was designed to match the bond- .
table: Level 3
table: Balance as of January 1, 2018 $278
table: Actual return on assets (23)
table: Purchases, issuances and settlements, net (25)
table: Balance as of December 31, 2018 $230
question: Analyse this data from a financial earnings document. by what percentage level 3 balance decrease during 2018?