What was the change in total deferred income tax expense between 2017 and 2019?
{"Current -- Federal": {"2019": 1615, "2018": 741, "2017": 584}, "Current -- State": {"2019": 900, "2018": 653, "2017": -88}, "Current -- Foreign": {"2019": 452, "2018": 263, "2017": 6}, "Current -- Total Current": {"2019": 2967, "2018": 1657, "2017": 502}, "Deferred -- Federal": {"2019": 2622, "2018": -8821, "2017": 3837}, "Deferred -- State": {"2019": -23, "2018": -2643, "2017": -1368}, "Deferred -- Foreign": {"2019": "\u2014", "2018": -18, "2017": 19}, "Deferred -- Total Deferred": {"2019": 2599, "2018": -11482, "2017": 2488}, "Deferred -- Total": {"2019": 5566, "2018": -9825, "2017": 2990}}
total_deferred_2019 = df["Deferred -- Total Deferred"]["2019"]
total_deferred_2017 = df["Deferred -- Total Deferred"]["2017"]
answer = total_deferred_2019 - total_deferred_2017