Fair Value Measurements - Narrative (Details) $ in Millions	3 Months Ended
Mar. 31, 2016 USD ($)
Level 3 \| iSIGHT Security
Debt Instrument [Line Items]
Earn-out period of performance	2 years 6 months
Level 3 \| Minimum \| iSIGHT Security
Debt Instrument [Line Items]
Quarterly revenue growth	30.00%
Discount rate	6.30%
Level 3 \| Maximum \| iSIGHT Security
Debt Instrument [Line Items]
Quarterly revenue growth	120.00%
Discount rate	7.10%
Level 3 \| Weighted Average \| iSIGHT Security
Debt Instrument [Line Items]
Expected volatility	16.50%
Fair Value Assumptions, Comparable Company Revenue Growth Correlated To Market	44.70%
Level 2 \| Convertible Senior Notes
Debt Instrument [Line Items]
Fair value of debt	$ 762.9

Fair Value Assumptions, Comparable Company Revenue Growth Correlated To Market

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Fair Value Assumptions, Revenue Volatility Rate

+ References

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- Definition

Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Convertible Security
-URI http://asc.fasb.org/extlink&oid=6509036

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Period the instrument, asset or liability is expected to be outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
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-URI http://asc.fasb.org/extlink&oid=66048111&loc=d3e19207-110258

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Interest rate used to find the present value of an amount to be paid or received in the future as an input to measure fair value. For example, but not limited to, weighted average cost of capital (WACC), cost of capital, cost of equity and cost of debt.

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Percentage of assumed long-term growth in revenues, used as an input to measure fair value.

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