What is the change in the amount of total goodwill in 2019 from 2018?
{"": {"2019": "", "2018": "(in millions)", "2017": ""}, "Cubic Transportation Systems": {"2019": 254.6, "2018": 49.8, "2017": 50.9}, "Cubic Mission Solutions": {"2019": 181.4, "2018": 138.1, "2017": "\u2014"}, "Cubic Global Defense": {"2019": 142.1, "2018": 145.7, "2017": 270.7}, "Total goodwill": {"2019": 578.1, "2018": 333.6, "2017": 321.6}}
total_goodwill_2019 = df["Total goodwill"]["2019"]
total_goodwill_2018 = df["Total goodwill"]["2018"]
answer = total_goodwill_2019 - total_goodwill_2018