Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

Fair Value of Financial Instruments Fair Value Measurements (Details) - Estimate of Fair Value Measurement - Foreign currency forward contracts - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Financial Assets Fair Value Disclosure
Foreign currency forward contracts	$ 508,000
Financial Liabilities Fair Value Disclosure
Foreign currency forward contracts		$ 94,000
Level 1
Financial Assets Fair Value Disclosure
Foreign currency forward contracts	0
Financial Liabilities Fair Value Disclosure
Foreign currency forward contracts		0
Level 2
Financial Assets Fair Value Disclosure
Foreign currency forward contracts	508,000
Financial Liabilities Fair Value Disclosure
Foreign currency forward contracts		94,000
Level 3
Financial Assets Fair Value Disclosure
Foreign currency forward contracts	$ 0
Financial Liabilities Fair Value Disclosure
Foreign currency forward contracts		$ 0