( 1 ) the weighted-average fair value of the shares granted during 2017 and 2016 was $ 59.12 and $ 37.35 , respectively . ( 2 ) the weighted-average fair value of the shares vesting during 2018 was approximately $ 77.65 per share . total unrecognized compensation cost related to unvested stock awards was $ 538 million at december 31 , 2018 . the cost is expected to be recognized over a weighted-average period of 1.7 years. .