Debt (Debt With A Contractual Term Greater Than One Year) (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, net	$ 6,463,466	$ 5,714,527
Current portion of long-term debt, net	(1,575,799)	(1,127,269)
Long-term debt	4,887,667	4,587,258
Secured Debt
Debt Instrument [Line Items]
Less: unamortized discount and debt issuance costs	(49)	(461)
Long-term debt, net	833,835	806,860
Secured Debt \| Asset-backed Canadian commercial paper conduit facility
Debt Instrument [Line Items]
Long-term Debt, Gross	155,951	174,779
Secured Debt \| Asset-Backed U.S. Commercial Paper Conduit Facility VIE
Debt Instrument [Line Items]
Long-term Debt, Gross	582,717	279,457
Secured Debt \| Term asset-backed securitization debt, VIE
Debt Instrument [Line Items]
Long-term Debt, Gross	95,216	353,085
Senior Unsecured Debt
Debt Instrument [Line Items]
Less: unamortized discount and debt issuance costs	(20,369)	(19,821)
Senior Unsecured Debt \| 6.80% Medium-term notes due 2018
Debt Instrument [Line Items]
Long-term Debt, Gross	0	$ 877,488
Stated interest rate		6.80%
Senior Unsecured Debt \| 2.40% Medium-term notes due 2019
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 600,000	$ 600,000
Stated interest rate	2.40%	2.40%
Senior Unsecured Debt \| 2.25% Medium-term notes due 2019
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 600,000	$ 600,000
Stated interest rate	2.25%	2.25%
Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2019 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 150,000	$ 150,000
Senior Unsecured Debt \| 2.15% Medium-term notes due 2020
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 600,000	$ 600,000
Stated interest rate	2.15%	2.15%
Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 450,000	$ 0
Senior Unsecured Debt \| Two Point Four Percent Medium-Term Notes Due 2020 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 350,000	$ 350,000
Stated interest rate	2.40%	2.40%
Senior Unsecured Debt \| Two Point Eighty-five Percent Medium-Term Notes Due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 600,000	$ 600,000
Stated interest rate	2.85%	2.85%
Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 450,000	$ 0
Senior Unsecured Debt \| Three Point Fifty-five Percent Medium Term Notes due 2021 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 350,000	0
Stated interest rate	3.55%
Senior Unsecured Debt \| Two Point Fifty-five Percent Medium-Term Notes Due 2022 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 400,000	$ 400,000
Stated interest rate	2.55%	2.55%
Senior Unsecured Debt \| Three Point Thirty-five Percent Medium Term Notes due 2023 [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 350,000	$ 0
Stated interest rate	3.35%
Senior Unsecured Debt \| 3.50% Senior unsecured notes due in 2025
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 450,000	$ 450,000
Stated interest rate	3.50%	3.50%
Senior Unsecured Debt \| 4.625% Senior unsecured notes due in 2045
Debt Instrument [Line Items]
Long-term Debt, Gross	$ 300,000	$ 300,000
Stated interest rate	4.625%	4.625%
London Interbank Offered Rate (LIBOR) [Member] \| Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2019 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.35%
London Interbank Offered Rate (LIBOR) [Member] \| Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.50%
London Interbank Offered Rate (LIBOR) [Member] \| Senior Unsecured Debt \| Floating-Rate Medium Term Notes due 2021 [Member]
Debt Instrument [Line Items]
Debt Instrument, Basis Spread on Variable Rate	0.94%

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

No definition available.

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
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+ Details

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- 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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-Section S99
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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

Amount of unamortized debt discount (premium) and debt issuance costs.

+ References

+ Details

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(3)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

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- Definition

Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt, classified as current. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

+ References

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- Definition

Amount after unamortized (discount) premium and debt issuance costs of long-term debt classified as noncurrent and excluding amounts to be repaid within one year or the normal operating cycle, if longer. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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