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Derivative Instruments and Risk Management Activities - Impact of Derivative Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivatives in Cash Flow Hedging Relationship
Amount of unrealized income (loss), net of tax, recognized in OCI	$ 6,546	$ 1,034	$ 1,728
Floorplan Interest Expense
Location of Income (Loss) Reclassified from OCI into Statements of Operations
Amount of loss reclassified from OCI into Statement of Operations	(4,671)	(10,272)	(11,097)
Other Interest Expense
Location of Income (Loss) Reclassified from OCI into Statements of Operations
Amount of loss reclassified from OCI into Statement of Operations	$ (476)	$ (1,924)	$ (2,332)

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- Definition

Derivatives in cash flow hedging relationship.

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Location of loss reclassified from other comprehensive income into statements of operations.

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Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

+ References

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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