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Financial Instruments and Fair Value Measurements - Impact of Interest Rate Derivative Instruments (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Derivative [Line Items] |  |  |  |
Amount of unrealized income (loss), net of tax, recognized in other comprehensive (loss) income | $ (5.6) |  | $ (19.2) |
Amount of unrealized income (loss), net of tax, recognized in other comprehensive (loss) income |  | $ 2.7 |  | $ 14.0
Floorplan interest expense, net |  |  |  |
Derivative [Line Items] |  |  |  |
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations |  |  | 0.4 |
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations |  |  |  | (4.0)
Other interest expense, net |  |  |  |
Derivative [Line Items] |  |  |  |
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations |  |  | $ 0.3 |
Amount of income (loss) reclassified from other comprehensive (loss) income into statements of operations |  |  |  | $ (0.5)

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