Derivative Investments and Hedging Activities (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015
Derivatives in Cash Flow Hedging Relationships [Abstract]
Loss related to effective portion of derivatives recognized in accumulated OCI, gross of tax effect	$ 110	$ 253
Loss related to effective portion of derivatives reclassified from accumulated OCI to interest expense, gross of tax effect	$ (507)	(354)
Cash Flow Hedging [Member]
Derivatives, Fair Value [Line Items]
Fixed interest rate	1.48%
Foreign Currency Exchange Contracts [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		284
Liabilities		48
Foreign Currency Exchange Contracts [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		0
Foreign Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		284
Foreign Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Foreign Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		48
Foreign Currency Exchange Contracts [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Long-Term Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		0
Interest Rate Swap Agreements [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Liabilities		397
Interest Rate Swap Agreements [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		397
Interest Rate Swap Agreements [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Interest Rate Swap Agreements [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Interest Rate Swap Agreements [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		0
Interest Rate Swap Agreements [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Long-Term Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		0
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member]
Fair Values of Derivative Instruments [Abstract]
Assets	$ 48,361	12,632
Liabilities	48,361	12,632
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities	0	0
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets	0	0
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets	48,361	12,632
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities	0	0
Cash Convertible Notes Hedges and Cash Conversion Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Long-Term Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities	48,361	12,632
Cash Convertible Notes Hedges [Member] \| Selling, General and Administrative Expenses [Member]
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net unrealized (loss) gain	35,729	(35,393)
Cash Conversion Derivative [Member] \| Selling, General and Administrative Expenses [Member]
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net unrealized (loss) gain	(35,729)	35,393
Gallup Derivative [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Liabilities		6,339
Gallup Derivative [Member] \| Loss from Discontinued Operation [Member]
Derivatives in Cash Flow Hedging Relationships [Abstract]
Net unrealized (loss) gain	$ 4,823	(7,325)
Gallup Derivative [Member] \| Derivatives Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		0
Gallup Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Current Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Gallup Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Assets [Member]
Fair Values of Derivative Instruments [Abstract]
Assets		0
Gallup Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Accrued Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		3,323
Gallup Derivative [Member] \| Derivatives Not Designated as Hedging Instruments [Member] \| Other Long-Term Liabilities [Member]
Fair Values of Derivative Instruments [Abstract]
Liabilities		$ 3,016

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Fair value, before 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 elected not to be offset. Excludes assets not subject to a master netting arrangement.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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Reference 4: http://www.xbrl.org/2003/role/presentationRef
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Fair value, before 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 elected not to be offset. Excludes liabilities not subject to a master netting arrangement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Fixed interest rate related to the interest rate derivative.

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The effective portion of loss reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying as hedging instruments.

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The effective portion of losses on derivative instruments designated and qualifying as hedging instruments that was recognized in other comprehensive income during the current period.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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