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

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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
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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

Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 470
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- Definition

Percentage of principal amount of debt redeemed.

+ References

No definition available.

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- Definition

Aggregate amount of interest paid or due on all long-term debt.

+ References

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- Definition

The cash outflow to repay long-term debt that is not secured by collateral. Excludes repayments of tax exempt unsecured debt.

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Debt and Credit Facilities - Senior Unsecured Notes (Narrative) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Sep. 30, 2017
2017 Senior Unsecured Notes Due in September 2018
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 750,000,000
2017 Senior Unsecured Notes Due in September 2019 with Floating Rate
Debt Instrument [Line Items]
Debt Instrument, Face Amount				500,000,000
2017 Senior Unsecured Notes Due in September 2019 with Fixed Rate
Debt Instrument [Line Items]
Debt Instrument, Face Amount				1,000,000,000.0
Term Loan Facilities
Debt Instrument [Line Items]
Interest Rate	1.85%
Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 3,000,000,000
Debt Instrument, Redemption Price, Percentage	100.00%
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	101.00%
Interest Expense, Long-term Debt	$ 1,100,000,000	$ 1,000,000,000	$ 907,000,000
Senior Unsecured Note Issued September 2017 [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Repayments of Unsecured Debt	750,000,000
Senior Unsecured Note Issued September 2015 [Member] \| Unsecured Debt [Member]
Debt Instrument [Line Items]
Repayments of Unsecured Debt	$ 1,000,000,000