Credit Agreement, Commercial Paper and Senior Notes - Senior Notes - Additional Information (Detail) $ in Millions	12 Months Ended
Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Unamortized discounts, net	$ 5.0
Debt issuance costs, net	$ 14.1
Minimum [Member] \| 5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
Maximum [Member] \| 5.15% Senior Notes due 2014 [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
3.45% Senior Notes due 2023 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
3.45% Senior Notes due 2023 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
4.875% Senior Notes due 2043 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
4.875% Senior Notes due 2043 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
4.875% Senior Notes due 2015 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
4.875% Senior Notes due 2015 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
5.875% Senior Notes due 2019 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
5.875% Senior Notes due 2019 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days
5.70% Senior Notes due 2039 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	15 days
5.70% Senior Notes due 2039 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Notice period for redemption of senior notes	60 days

Mandatory notification period to note holders giving written prior notice of the entity's intention to redeem all or a portion of the indebtedness.

No definition available.

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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.

+ Details

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- Definition

Amount, after accumulated amortization, of debt discount.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 1A
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28541-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.17)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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