Derivative Instruments, Hedging Activities and Fair Value (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jan. 01, 2018	Dec. 31, 2017
Derivative contracts
Liabilities	$ 1,345,259	$ 1,325,152	$ 1,363,520
Subject to Master Netting Agreements [Member]
Derivative contracts
Net Assets	1,100
Liabilities			200
Designated as hedging instrument
Derivative contracts
Asset Derivatives	6,948		2,963
Liability Derivatives	742		1,521
Designated as hedging instrument | Foreign currency forward exchange contracts | Other current assets
Derivative contracts
Asset Derivatives	2,183		2,329
Designated as hedging instrument | Foreign currency forward exchange contracts | Other current liabilities
Derivative contracts
Liability Derivatives	389		153
Designated as hedging instrument | Interest rate swaps | Other current assets
Derivative contracts
Asset Derivatives	1,623		464
Designated as hedging instrument | Interest rate swaps | Other Noncurrent Assets [Member]
Derivative contracts
Asset Derivatives	3,142		170
Designated as hedging instrument | Interest rate swaps | Other current liabilities
Derivative contracts
Liability Derivatives
Designated as hedging instrument | Interest rate swaps | Other liabilities
Derivative contracts
Liability Derivatives	353		1,368
Derivatives Not Designated as Hedging Instruments | Foreign currency forward exchange contracts | Other current assets
Derivative contracts
Asset Derivatives	11,567		2,915
Derivatives Not Designated as Hedging Instruments | Foreign currency forward exchange contracts | Other current liabilities
Derivative contracts
Liability Derivatives	$ 2,415		$ 6,970