. as of september 30 , 2018 and 2017 , the total amount of unrecognized tax benefits was approximately $ 127.1 million and $ 148.9 million , respectively , exclusive of interest and penalties . of these balances , as of september 30 , 2018 and 2017 , if we were to prevail on all unrecognized tax benefits recorded , approximately $ 108.7 million and $ 138.0 million , respectively , would benefit the effective tax rate