Fair Value Measurements and Derivative Instruments (Derivative Instruments) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2016
Derivative [Line Items]
Total net derivative liability	$ 1,563,000	$ (1,492,000)
Total derivative assets
Derivative [Line Items]
Derivative asset	1,898,000	2,225,000
Total derivative liabilities
Derivative [Line Items]
Derivative liability	(335,000)	(3,717,000)
Foreign exchange contracts | Derivatives designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Derivative asset	57,000	487,000
Foreign exchange contracts | Derivatives designated as hedging instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative liability	(144,000)	(136,000)
Foreign exchange contracts | Derivatives not designated as hedging instruments | Other current assets and prepayments
Derivative [Line Items]
Derivative asset	65,000	150,000
Foreign exchange contracts | Derivatives not designated as hedging instruments | Accounts payable and accrued liabilities
Derivative [Line Items]
Derivative liability	(191,000)	(3,581,000)
Interest rate swap | Derivatives designated as hedging instruments | Other non-current assets
Derivative [Line Items]
Derivative asset	1,776,000	1,588,000
Cash Flow Hedging
Derivative [Line Items]
Total notional amount of outstanding contracts	$ 10,000,000	$ 13,000,000
Cash Flow Hedging | Interest rate contract
Derivative [Line Items]
Total notional amount of outstanding contracts			$ 300,000,000
Fixed interest rate			0.8826%