Stock-Based Compensation - Summary Of Changes In RSUs Outstanding (Details) shares in Millions	9 Months Ended
Sep. 30, 2017 $ / shares shares
Restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Restricted Stock Units (RSUs) [Roll Forward]
Outstanding at December 31, 2016 (in shares)	1.3
Granted (in shares)	1.1
Vested and released (in shares)	(0.7)
Forfeited (in shares)	(0.1)
Outstanding at September 30, 2017 (in shares)	1.6
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Outstanding at December 31, 2016 (in dollars per share) \| $ / shares	$ 73.19
Granted (in dollars per share) \| $ / shares	105.45
Vested and released (in dollars per share) \| $ / shares	78.44
Forfeited (in dollars per share) \| $ / shares	93.18
Outstanding at September 30, 2017 (in dollars per share) \| $ / shares	$ 91.37
Weighted average remaining contractual terms	1 year 4 months 24 days
Restricted stock units \| Executive officer
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.2
Restricted stock units \| Executive officer \| Minimum \| Target amount
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Percentage of shares authorized for grant	0.00%
Restricted stock units \| Executive officer \| Maximum \| Target amount
Per Share Weighted Average Grant Date Fair Value [Roll Forward]
Percentage of shares authorized for grant	200.00%
Restricted stock units \| Non executive
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.9
Performance-based RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
CEB \| Restricted stock units
Restricted Stock Units (RSUs) [Roll Forward]
Granted (in shares)	0.6

Share Based Compensation Arrangement by Share Based Payment Award Percentage of Shares Authorized for Grant.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested and Released in Period.

+ References

No definition available.

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Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other Than Options Vested And Released In Period Weighted Average Grant Date Fair Value.

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No definition available.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, 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 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iv)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(3)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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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.

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- Definition

The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5070-113901

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

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- Definition

Weighted average remaining contractual term for equity-based awards excluding options, 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 718
-SubTopic 10
-Section 50
-Paragraph 2
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- Definition

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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