Fair Value of Financial Instruments (Details) - Senior Notes - USD ($)	Sep. 30, 2018	Aug. 28, 2018
$700 3.650% senior notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face value of debt		$ 700,000,000
Interest rate on senior notes		3.65%
$800 4.200% senior notes due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Face value of debt		$ 800,000,000
Interest rate on senior notes		4.20%
Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fixed rate senior notes carrying amount	$ 4,900,000,000
Fair Value, Inputs, Level 2 \| $800 2.050% senior notes due 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	800,000,000
Face value of debt	$ 800,000,000
Interest rate on senior notes	2.05%
Fair Value, Inputs, Level 2 \| $600 3.000% senior notes due 2020
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 597,000,000
Face value of debt	$ 600,000,000
Interest rate on senior notes	3.00%
Fair Value, Inputs, Level 2 \| $500 2.800% senior notes due 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 490,000,000
Face value of debt	$ 500,000,000
Interest rate on senior notes	2.80%
Fair Value, Inputs, Level 2 \| $500 3.125% senior notes due 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 488,000,000
Face value of debt	$ 500,000,000
Interest rate on senior notes	3.125%
Fair Value, Inputs, Level 2 \| $700 3.650% senior notes due 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 697,000,000
Face value of debt	$ 700,000,000
Interest rate on senior notes	3.65%
Fair Value, Inputs, Level 2 \| $300 3.850% senior notes due 2025
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 295,000,000
Face value of debt	$ 300,000,000
Interest rate on senior notes	3.85%
Fair Value, Inputs, Level 2 \| $700 3.800% senior notes due 2026
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 683,000,000
Face value of debt	$ 700,000,000
Interest rate on senior notes	3.80%
Fair Value, Inputs, Level 2 \| $800 4.200% senior notes due 2028
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Long-term debt, fair value	$ 795,000,000
Face value of debt	$ 800,000,000
Interest rate on senior notes	4.20%

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

Reference 1: 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

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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