Derivative Instruments and Hedging Activities (Details) $ in Thousands, € in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2018 EUR (€)	Sep. 30, 2018 EUR (€)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2016 EUR (€)
Effect of Netting Derivative Instruments		$ (19,000)	$ (19,000)			$ (12,000)
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net		4,000	4,000
Settlement of Notional Amounts | €					€ (15)
Derivative Asset, Noncurrent		36,600	36,600			24,606
Derivative Liability, Noncurrent		49,212	49,212			61,492
Interest Rate Swap [Member]
Derivative, Notional Amount		590,000	590,000			590,000
Derivative Asset, Noncurrent		25,719	25,719			19,102
Cross Currency Interest Rate Contract [Member]
Derivative, Notional Amount		394,649	394,649			406,546	$ 422,000	€ 400
Derivative Asset, Noncurrent		10,881	10,881			5,504
Derivative Liability, Noncurrent		49,212	49,212			$ 61,492
Right to acquire equity method investment [Domain] | Mekonomen [Member]
Derivative Asset, Noncurrent		29,000	29,000
Fair Value, Measured on Recurring Basis, Gain (Loss) Included in Earnings	$ 8,000	$ (2,509)	$ (2,509)
2018 Cross Currency Swaps [Member] | Cross Currency Interest Rate Contract [Member]
Derivative, Notional Amount	$ 184,000			€ 160