What was the increase / (decrease) in the total company debt from 2018 to 2019?
{"($ in millions) -- At December 31:": {"2019": 2019, "2018": 2018}, "($ in millions) -- Total company debt": {"2019": 62899, "2018": 45812}, "($ in millions) -- Total Global Financing segment debt": {"2019": 24727, "2018": 31227}, "($ in millions) -- Debt to support external clients": {"2019": 21487, "2018": 27536}, "($ in millions) -- Debt to support internal clients": {"2019": 3239, "2018": 3690}, "($ in millions) -- Non-Global Financing debt": {"2019": 38173, "2018": 14585}}
total_company_debt_2019 = df["($ in millions) -- Total company debt"]["2019"]
total_company_debt_2018 = df["($ in millions) -- Total company debt"]["2018"]
answer = total_company_debt_2019 - total_company_debt_2018