What was the change in the cash and cash equivalents from 2018 to 2019?
{"(in thousands) -- Cash and cash equivalents": {"December 31, 2019": 92708, "December 31, 2018": 73142}, "(in thousands) -- Short-term restricted cash": {"December 31, 2019": 349, "December 31, 2018": 645}, "(in thousands) -- Long-term restricted cash": {"December 31, 2019": 60, "December 31, 2018": 404}, "(in thousands) -- Total cash, cash equivalents and restricted cash": {"December 31, 2019": 93117, "December 31, 2018": 74191}}
cash_2019 = df["(in thousands) -- Cash and cash equivalents"]["December 31, 2019"]
cash_2018 = df["(in thousands) -- Cash and cash equivalents"]["December 31, 2018"]
answer = cash_2019 - cash_2018