Derivative Instruments, Hedging Activities and Fair Value - Fair Value of Outstanding Derivative Contracts (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
Derivative contracts
Asset derivatives	$ 15,304	$ 5,878
Liability derivatives	1,723	8,491
Foreign currency exchange forward contracts | Other current assets
Derivative contracts
Asset derivatives	9,951	5,244
Foreign currency exchange forward contracts | Other current liabilities
Derivative contracts
Liability derivatives	1,692	7,123
Interest rate swaps | Other current assets
Derivative contracts
Asset derivatives	1,900	464
Interest rate swaps | Other assets
Derivative contracts
Asset derivatives	3,453	170
Interest rate swaps | Other liabilities
Derivative contracts
Liability derivatives	31	1,368
Fair Value of Derivatives Designated as Hedging Instruments
Derivative contracts
Asset derivatives	7,562	2,963
Liability derivatives	140	1,521
Fair Value of Derivatives Designated as Hedging Instruments | Foreign currency exchange forward contracts | Other current assets
Derivative contracts
Asset derivatives	2,209	2,329
Fair Value of Derivatives Designated as Hedging Instruments | Foreign currency exchange forward contracts | Other current liabilities
Derivative contracts
Liability derivatives	109	153
Fair Value of Derivatives Designated as Hedging Instruments | Interest rate swaps | Other current assets
Derivative contracts
Asset derivatives	1,900	464
Fair Value of Derivatives Designated as Hedging Instruments | Interest rate swaps | Other assets
Derivative contracts
Asset derivatives	3,453	170
Fair Value of Derivatives Designated as Hedging Instruments | Interest rate swaps | Other liabilities
Derivative contracts
Liability derivatives	31	1,368
Fair Value of Derivatives Not Designated as Hedging Instruments
Derivative contracts
Asset derivatives	7,742	2,915
Liability derivatives	1,583	6,970
Fair Value of Derivatives Not Designated as Hedging Instruments | Foreign currency exchange forward contracts | Other current assets
Derivative contracts
Asset derivatives	7,742	2,915
Fair Value of Derivatives Not Designated as Hedging Instruments | Foreign currency exchange forward contracts | Other current liabilities
Derivative contracts
Liability derivatives	1,583	6,970
Fair Value of Derivatives Not Designated as Hedging Instruments | Interest rate swaps | Other current assets
Derivative contracts
Asset derivatives	0	0
Fair Value of Derivatives Not Designated as Hedging Instruments | Interest rate swaps | Other assets
Derivative contracts
Asset derivatives	0	0
Fair Value of Derivatives Not Designated as Hedging Instruments | Interest rate swaps | Other liabilities
Derivative contracts
Liability derivatives	$ 0	$ 0