Income Taxes - Valuation Allowance for Deferred Tax Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Valuation Allowances and Reserves [Roll Forward]
Beginning of year balance	$ 365,035	$ 250,164	$ 136,547
Changes in valuation allowance charged to income	36,639	114,980	114,106
Change in enacted tax rates	(137,001)	0	0
Foreign currency translation	689	(109)	(773)
Acquisition	0	0	284
End of year balance	$ 265,362	$ 365,035	$ 250,164

Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Charged To Income

No definition available.

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- Definition

Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount Due To Change In Enacted Tax Rate

+ References

No definition available.

+ Details

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- Definition

Amount of deferred tax assets for which it is more likely than not that a tax benefit will not be realized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65882285&loc=d3e32537-109319

+ Details

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- Definition

The amount of the valuation allowance recorded in a business combination against deductible temporary differences for which related tax benefits will be recorded as a reduction of the acquired entity's income tax expense (after such benefits are first being applied to reduce goodwill and then other noncurrent intangible assets to zero).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 740
-Section 25
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6912350&loc=d3e9901-128506

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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- Definition

Amount of increase (decrease) in the valuation allowance for a specified deferred tax asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 45
-Paragraph 20
-URI http://asc.fasb.org/extlink&oid=75116654&loc=d3e32123-109318

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