Indebtedness - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Debt, aggregate principal amount	$ 4,098.8	$ 3,377.4
Commercial Paper [Member]
Debt Instrument [Line Items]
Senior unsecured revolving credit facility	1,000.0
Debt, aggregate principal amount	$ 214.0
Issuance Date of Debt	Aug. 03, 2016
Commercial paper, interest rate	1.29%
Commercial Paper [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Term of notes	397 days
Commercial Paper [Member] \| Weighted Average Interest Rate [Member]
Debt Instrument [Line Items]
Term of notes	20 days
2017 Floating Rate Senior Notes [Member]
Debt Instrument [Line Items]
Debt, aggregate principal amount	$ 300.0
Maturity date of Senior Unsecured Notes	Sep. 04, 2018
Issuance Date of Debt	Mar. 02, 2017
Debt aggregate amount for default in principal, interest or fail to pay	$ 50.0
Percentage of principal amount being prepaid plus accrued and unpaid interest	100.00%
Percentage of Principal Amount Plus Accrued and Unpaid Interest to Date of Purchase	101.00%
Minimum Percentage of Aggregate Principal Amount	25.00%
Percentage Included in Calculation of Senior Notes Floating Rate Plus LIBOR	0.35%
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Debt, aggregate principal amount	$ 500.0
Senior Unsecured Notes, interest	2.75%
Maturity date of Senior Unsecured Notes	Dec. 15, 2021
Issuance Date of Debt	Mar. 02, 2017
Debt aggregate amount for default in principal, interest or fail to pay	$ 50.0
Percentage of principal amount being prepaid plus accrued and unpaid interest	100.00%
Percentage of Principal Amount Plus Accrued and Unpaid Interest to Date of Purchase	101.00%
Minimum Percentage of Aggregate Principal Amount	25.00%
Series 2007-1 Notes [Member]
Debt Instrument [Line Items]
Prepayment penalities of notes	$ 7.0

Floating Rate equals of 3-Month LIBOR at time of interest payment plus 0.35%.

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- Definition

Minimum percentage of votes needed by holders of the notes which will result in the notes becoming due and payable pursuant to an event of default.

+ References

No definition available.

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- Definition

Amount the Company would need to repay in the event of a "Change of Control Triggering Event" in relation to it's outstanding indebtedness.

+ References

No definition available.

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- Definition

Percentage of principal amount that the Company would be required to pay upon the occurrence of a "Change in Control Triggering Event as defined in the note agreements".

+ References

No definition available.

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- Definition

Date the original debt was issued, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
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- Definition

Amount of outstanding long-term debt or borrowing associated with any securities or credit agreement for which there has been a default in principal, interest, sinking fund, or redemption provisions, or any breach of covenant that existed at the end of the period and subsequently has not been cured.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08.(c))
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- Definition

Face (par) amount of debt instrument at time of issuance.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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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.

+ References

No definition available.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

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-Publisher FASB
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- Definition

The cash outflow for incremental, external costs directly pertaining to an early extinguishment of debt, including legal costs and prepayment penalties, and excluding interest and repayment of debt principal.

+ References

No definition available.

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- Definition

Weighted average interest rate of short-term debt outstanding.

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