Market Risks and Derivative Hedge Contracts (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Derivatives, Fair Value [Line Items]
Total	$ 114,000		$ 114,000		$ 290,000
Derivative [Line Items]
Net gains associated with foreign currency derivatives	100,000	$ (400,000)	1,200,000	$ (1,600,000)
Forward Purchase Contract, Euro [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 1,879,000		$ 1,879,000
Traded exchange rate	1.20		1.20
Value date	Oct. 18, 2017
Forward Purchase Contract, Pounds Sterling [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 6,980,000		$ 6,980,000
Traded exchange rate	1.32		1.32
Value date	Oct. 18, 2017
Forward Purchase Contract, Brazil Real [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 3,270,000		$ 3,270,000
Traded exchange rate	1.22		1.22
Value date	Oct. 18, 2017
Forward Purchase Contract, Mexican Pesos [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 6,951,000		$ 6,951,000
Traded exchange rate	17.93		17.93
Value date	Oct. 18, 2017
Forward Sale Contract, Norwegian Krone [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 3,009,000		$ 3,009,000
Traded exchange rate	7.88		7.88
Value date	Oct. 18, 2017
Forward Sale Contract, Mexican Pesos (2) [Member]
Derivative [Line Items]
U.S. Dollar notional amount	$ 5,088,000		$ 5,088,000
Traded exchange rate	17.93		17.93
Value date	Oct. 18, 2017
Current Assets [Member]
Derivatives, Fair Value [Line Items]
Forward purchase contracts	$ 88,000		$ 88,000		0
Forward sale contracts	187,000		187,000		81,000
Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Forward purchase contracts	$ (161,000)		$ (161,000)		$ (371,000)