Income Taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2009
Income Tax Contingency [Line Items]
Effective income tax rate reconciliation, at federal statutory income tax rate	30.90%	25.30%
Federal statutory rate	35.00%jnpr_FederalStatutoryRate	35.00%jnpr_FederalStatutoryRate
Tax on equity investments	$ 0	$ 35.6
Restructuring	(1.3)	(30.8)
Valuation allowance release related to gain on sale of equity investments	24.7
Unrecognized tax benefits	201.3us-gaap_UnrecognizedTaxBenefits
Unrecognized tax benefits that would impact effective tax rate	167.3
Foreign country
Income Tax Contingency [Line Items]
Interest and penalties recorded			4.6
Maximum [Member]
Income Tax Contingency [Line Items]
Greater than remote likelihood decrease in gross unrecognized tax benefits within next 12 months	$ 3.1

Effective Tax Reconciliation , Tax on gain of equity investments, Amount

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Federal Statutory Rate

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- Definition

Valuation allowance release related to gain on sale of equity investments

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- Definition

Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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The amount of estimated penalties and interest accrued as of the balance sheet date arising from income tax examinations.

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Amount of the difference between reported income tax expense (benefit) and the expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to deduction for qualified production activity.

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The amount of the unrecognized tax benefit of a position taken for which it is reasonably possible that the total amount thereof will significantly increase or decrease within twelve months of the balance sheet date.

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Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

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-Glossary Unrecognized Tax Benefit

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The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

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