Fair Value Measurement and Fair Value of Financial Instruments (Detail) - Senior Notes - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
4.375% Senior Notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate (as a percent)	4.375%
3.45% Senior Notes due 2026
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate (as a percent)	3.45%
4.15% Senior Notes due 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate (as a percent)	4.15%
4.7% Senior Notes due 2028
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Stated interest rate (as a percent)	4.70%
Carrying Value \| 4.375% Senior Notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	$ 249.0	$ 248.8
Carrying Value \| 3.45% Senior Notes due 2026
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	748.5	748.2
Carrying Value \| Floating Rate Notes due 2021
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	497.7	496.8
Carrying Value \| 4.15% Senior Notes due 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	744.0	743.0
Carrying Value \| 4.7% Senior Notes due 2028
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	1,240.5	1,239.7
Fair Value \| 4.375% Senior Notes due 2023
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	262.4	254.2
Fair Value \| 3.45% Senior Notes due 2026
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	758.3	675.1
Fair Value \| Floating Rate Notes due 2021
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	500.0	497.4
Fair Value \| 4.15% Senior Notes due 2024
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	799.3	729.4
Fair Value \| 4.7% Senior Notes due 2028
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt instrument	$ 1,378.4	$ 1,179.6

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 10
-URI http://asc.fasb.org/extlink&oid=118260190&loc=d3e13433-108611

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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+ References

No definition available.

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