Percentage points added to the reference rate to compute the variable rate on the debt instrument.

No definition available.

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- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
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+ Details

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Period Type:	instant

- Definition

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

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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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

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.

+ Details

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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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
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Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
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-Paragraph 14
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- Definition

Amount of cash inflow from contractual arrangement with the lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

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-Publisher FASB
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Debt - Additional Information (Detail) - USD ($)	1 Months Ended			12 Months Ended
Debt - Additional Information (Detail) - USD ($)	Oct. 31, 2018	Mar. 31, 2018	Apr. 30, 2017	Dec. 31, 2018	Dec. 31, 2017
Discretionary Line of Credit
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity				$ 250,000,000
Debt Instrument, Term				30 days
Proceeds from Lines of Credit				$ 0	$ 0
4.00% Senior Notes due 2029
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 550,000,000			$ 550,000,000	0
Debt Instrument, Interest Rate, Stated Percentage	4.00%			4.00%
Proceeds from Debt, Net of Issuance Costs	$ 544,500,000
4.20% Senior Notes due 2048
Debt Instrument [Line Items]
Debt Instrument, Face Amount		$ 600,000,000		$ 600,000,000	0
Debt Instrument, Interest Rate, Stated Percentage		4.20%		4.20%
Proceeds from Debt, Net of Issuance Costs		$ 589,500,000
4.125% Senior Notes due 2047
Debt Instrument [Line Items]
Debt Instrument, Face Amount			$ 850,000,000	$ 850,000,000	$ 850,000,000
Debt Instrument, Interest Rate, Stated Percentage			4.125%	4.125%
Proceeds from Debt, Net of Issuance Costs			$ 841,100,000
Federal Funds Rate [Member] \| Discretionary Line of Credit
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate				0.50%