Derivative Financial Instruments Derivative and Nonderivative Hedging Instrument Fair Value Disclosure (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Asset Derivatives [Abstract]
Derivative Asset	$ 2,900	$ 2,945
Liability Derivatives [Abstract]
Derivative Liability	289	1,383
Designated as Hedging Instrument [Member] \| Other Noncurrent Assets [Member] \| Interest Rate Cap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	179	376
Designated as Hedging Instrument [Member] \| Other Noncurrent Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	1,712	1,830
Designated as Hedging Instrument [Member] \| Other Current Assets [Member] \| Interest Rate Cap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	17	3
Designated as Hedging Instrument [Member] \| Other Current Assets [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Derivative Assets, at Fair Value	658	0
Designated as Hedging Instrument [Member] \| Other Current Liabilities [Member] \| Interest Rate Swap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	0	934
Not Designated as Hedging Instrument [Member] \| Other Noncurrent Assets [Member] \| Interest Rate Cap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	268	563
Not Designated as Hedging Instrument [Member] \| Other Current Assets [Member]
Asset Derivatives [Abstract]
Foreign exchange forward contracts	41	169
Not Designated as Hedging Instrument [Member] \| Other Current Assets [Member] \| Interest Rate Cap [Member]
Derivatives, Fair Value [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	25	4
Not Designated as Hedging Instrument [Member] \| Other Current Liabilities [Member]
Liability Derivatives [Abstract]
Foreign exchange forward contracts	$ 289	$ 449

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.

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-Name Accounting Standards Codification
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Fair value, after the effects of master netting arrangements, of a financial liability or 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 liabilities not subject to a master netting arrangement and not elected to be offset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Fair value as of the balance sheet date of all foreign currency derivative assets not designated as hedging instruments.

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Fair value as of the balance sheet date of all foreign currency derivative liabilities not designated as hedging instruments.

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Fair value as of the balance sheet date of all interest rate derivative assets designated as cash flow hedging instruments.

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Fair value as of the balance sheet date of interest rate derivative assets, which includes all such derivative instruments in hedging and nonhedging relationships that are recognized as assets.

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