What was the change in Total debt in 2019 from 2018?
{"Senior unsecured notes, 5.20% due July 2021 (face value of $250.0 million at June 30, 2019 and 2018)": {"2019": 251.2, "2018": 246.6}, "Senior unsecured notes, 4.45% due March 2023 (face value of $300.0 million at June 30, 2019 and 2018)": {"2019": 299.4, "2018": 299.1}, "Total": {"2019": 550.6, "2018": 545.7}, "Less: amounts due within one year": {"2019": "\u2014", "2018": "\u2014"}, "Long-term debt, net of current portion": {"2019": 550.6, "2018": 545.7}}
total_2019 = df["Total"]["2019"]
total_2018 = df["Total"]["2018"]
answer = total_2019 - total_2018