Derivatives - Income Statement (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Interest Rate Swaps \| Designated Hedges \| Fair Value Hedges \| Other (expense) income, net
Income Statement Location and Income (Expense)
Effectiveness	$ (605)	$ (540)	$ 1,646
Ineffectiveness	1,032	(1,280)	232
Foreign Currency Forward Contracts \| Non-designated Hedges \| Foreign exchange (loss) gain, net
Income Statement Location and Income (Expense)
Realized gains (losses)	(21,870)	16,873	(16,651)
Foreign Currency Forward Contracts \| Designated Hedges \| Cash Flow Hedging \| Service revenue
Income Statement Location and Income (Expense)
Realized gains (losses)	$ (1,744)	$ 5,218	$ 244

Amount of gain (loss)recognized in the income statement from the hedging effectiveness of a fair value hedge.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5618551-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=84234895&loc=SL5624171-113959

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+ References

No definition available.

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Amount of gain (loss)recognized in the income statement from the hedging ineffectiveness of a fair value hedge.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 25
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=6886632&loc=d3e76258-113986

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