Derivatives and Hedging - Outstanding Derivatives Contracts (Details) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2018 USD ($) outstanding_contract	Dec. 31, 2017 USD ($) outstanding_contract
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	51	142
Notional Amounts	$ 1,713,425	$ 2,086,764
Fair Value Asset (Liability), Net	16,819	3,860
Unrealized Gain Recorded in AOCI/L	$ 12,597	$ 2,483
Designated as hedging instrument \| Other assets \| Interest rate swaps
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	5	5
Notional Amounts	$ 1,400,000	$ 1,400,000
Fair Value Asset (Liability), Net	17,314	3,412
Unrealized Gain Recorded in AOCI/L	$ 12,597	$ 2,483
Not Designated as Hedging Instrument \| Accrued liabilities \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract	46
Notional Amounts	$ 313,425
Fair Value Asset (Liability), Net	(495)
Unrealized Gain Recorded in AOCI/L	$ 0
Not Designated as Hedging Instrument \| Other current assets \| Foreign currency forwards
Derivatives, Fair Value [Line Items]
Number of Outstanding Contracts \| outstanding_contract		137
Notional Amounts		$ 686,764
Fair Value Asset (Liability), Net		448
Unrealized Gain Recorded in AOCI/L		$ 0

Aggregate notional amount specified by the derivative(s). Expressed as an absolute value.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 13
-Sentence Column B

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- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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- Definition

The number of derivative instruments of a particular group held by the entity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1B
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5580258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 1A
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5579245-113959

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+ References

No definition available.

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