Debt (Debt With A Contractual Term Greater Than One Year) (Detail) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Apr. 01, 2018
Debt Instrument
Gross long-term debt	$ 6,116,744	$ 6,463,466	$ 5,981,190
Less: current portion of long-term debt, net of unamortized discount and debt issuance costs	(1,372,050)	(1,575,799)	(1,872,679)
Long-term debt, net	4,744,694	4,887,667	4,108,511
Secured Debt
Debt Instrument
Less: unamortized discount and debt issuance costs	(18)	(49)	(337)
Gross long-term debt	688,317	833,835	724,266
Secured Debt \| Asset-backed Canadian commercial paper conduit facility
Debt Instrument
Long-term debt, gross	142,676	155,951	158,162
Secured Debt \| Asset-Backed U.S. Commercial Paper Conduit Facility VIE
Debt Instrument
Long-term debt, gross	526,947	582,717	281,311
Secured Debt \| Asset-backed securitization debt
Debt Instrument
Long-term debt, gross	18,712	95,216	285,130
Unsecured Debt
Debt Instrument
Less: unamortized discount and debt issuance costs	(21,573)	(20,369)	(20,564)
Unsecured Debt \| 6.80% Medium-term notes due in 2018, issued May 2008
Debt Instrument
Long-term debt, gross	0	0	877,488
Unsecured Debt \| 2.25% Medium-term notes due in 2019, issued January 2016
Debt Instrument
Long-term debt, gross	0	600,000	600,000
Unsecured Debt \| Floating-Rate Medium Term Notes due 2019
Debt Instrument
Long-term debt, gross	0	150,000	150,000
Unsecured Debt \| Two Point Four Percent Medium-Term Notes Due 2019
Debt Instrument
Long-term debt, gross	$ 600,000	600,000	600,000
Debt instrument, stated percentage	2.40%
Unsecured Debt \| 2.15% Medium-term notes due in 2020, issued February 2015
Debt Instrument
Long-term debt, gross	$ 600,000	600,000	600,000
Debt instrument, stated percentage	2.15%
Unsecured Debt \| Floating-Rate Medium Term Notes due 2020
Debt Instrument
Long-term debt, gross	$ 450,000	450,000	0
Debt instrument, stated percentage	0.50%
Unsecured Debt \| Two Point Four Percent Medium-Term Notes Due 2020
Debt Instrument
Long-term debt, gross	$ 350,000	350,000	350,000
Debt instrument, stated percentage	2.40%
Unsecured Debt \| Two Point Eighty-five Percent Medium-Term Notes Due 2021
Debt Instrument
Long-term debt, gross	$ 600,000	600,000	600,000
Debt instrument, stated percentage	2.85%
Unsecured Debt \| Floating-Rate Medium Term Notes due 2021
Debt Instrument
Long-term debt, gross	$ 450,000	450,000	0
Debt instrument, stated percentage	0.94%
Unsecured Debt \| Three Point Fifty-five Percent Medium-Term Notes due 2021
Debt Instrument
Long-term debt, gross	$ 350,000	350,000	0
Debt instrument, stated percentage	3.55%
Unsecured Debt \| Four Point Zero-five Percent Medium Term Notes Due 2019
Debt Instrument
Long-term debt, gross	$ 550,000	0	0
Debt instrument, stated percentage	2.85%
Unsecured Debt \| Two Point Fifty-five Percent Medium-Term Notes Due 2022
Debt Instrument
Long-term debt, gross	$ 400,000	400,000	400,000
Debt instrument, stated percentage	2.55%
Unsecured Debt \| Three Point Thirty-five Percent Medium Term Notes Due 2023
Debt Instrument
Long-term debt, gross	$ 350,000	350,000	350,000
Debt instrument, stated percentage	3.35%
Unsecured Debt \| Three Point Five Percent Senior Unsecured Notes Due 2025
Debt Instrument
Long-term debt, gross	$ 450,000	450,000	450,000
Debt instrument, stated percentage	3.50%
Unsecured Debt \| Four Point Six Two Five Percent Senior Unsecured Notes Due 2045
Debt Instrument
Long-term debt, gross	$ 300,000	$ 300,000	$ 300,000
Debt instrument, stated percentage	4.625%

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.

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)(1)
-URI http://asc.fasb.org/extlink&oid=109500613&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

+ Details

Name:	us-gaap_DebtInstrumentCarryingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_DebtInstrumentInterestRateStatedPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnamortizedDiscountPremiumAndDebtIssuanceCostsNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- 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

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19,20)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- 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.

+ 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
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_LongTermDebtNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant