Fair Value Measurement (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ 21,268	$ 2,104
Other Contract [Member] | Other Expense [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Instruments Not Designated as Hedging Instruments, Gain (Loss), Net	$ (20,200)
Level III [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value Inputs, Discount for Lack of Marketability	32.00%