Debt - Summary of Unsecured Senior Notes (Details)	3 Months Ended
Mar. 31, 2018 USD ($)	Mar. 31, 2018 EUR (€)	Dec. 31, 2017 USD ($)
Senior Unsecured Notes
Unsecured senior notes, net	$ 3,115,839,000		$ 2,474,661,000
Deferred financing costs	19,553,000
Unamortized discount, net	15,786,000
Senior Unsecured Notes
Senior Unsecured Notes
Principal Amount	3,100,000,000.0
Unsecured senior notes, net	3,148,300,000		2,499,400,000
Deferred financing costs	18,500,000		14,700,000
Unamortized discount, net	$ 13,800,000		9,900,000
Senior Unsecured Notes \| 2.0% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	2.00%	2.00%
Issue Date	Jan. 21, 2015
Principal Amount \| €		€ 500,000,000
Price of Par Value	99.22%	99.22%
Discount	$ 4,600,000
Effective Interest Rate	2.107%	2.107%
Coupon Rate	2.00%
Maturity Date	Jan. 20, 2023
Unsecured senior notes, net	$ 616,100,000		599,700,000
Senior Unsecured Notes \| 4.6% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	4.60%	4.60%
Issue Date	Mar. 14, 2014
Principal Amount	$ 500,000,000
Price of Par Value	99.639%	99.639%
Discount	$ 1,800,000
Effective Interest Rate	4.645%	4.645%
Coupon Rate	4.60%
Maturity Date	Apr. 01, 2024
Unsecured senior notes, net	$ 500,000,000		500,000,000
Senior Unsecured Notes \| 2.25% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	2.25%	2.25%
Issue Date	Jan. 19, 2017
Principal Amount \| €		€ 500,000,000
Price of Par Value	99.448%	99.448%
Discount	$ 2,900,000
Effective Interest Rate	2.332%	2.332%
Coupon Rate	2.25%
Maturity Date	Jul. 19, 2024
Unsecured senior notes, net	$ 616,100,000		599,700,000
Deferred financing costs	$ 4,300,000
Senior Unsecured Notes \| 4.0% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	4.00%	4.00%
Issue Date	Jan. 26, 2015
Principal Amount	$ 450,000,000
Price of Par Value	99.372%	99.372%
Discount	$ 2,800,000
Effective Interest Rate	4.077%	4.077%
Coupon Rate	4.00%
Maturity Date	Feb. 01, 2025
Unsecured senior notes, net	$ 450,000,000		450,000,000
Senior Unsecured Notes \| 4.25% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	4.25%	4.25%
Issue Date	Sep. 12, 2016
Principal Amount	$ 350,000,000
Price of Par Value	99.682%	99.682%
Discount	$ 1,100,000
Effective Interest Rate	4.29%	4.29%
Coupon Rate	4.25%
Maturity Date	Oct. 01, 2026
Unsecured senior notes, net	$ 350,000,000		350,000,000
Senior Unsecured Notes \| 2.125% Senior Notes
Senior Unsecured Notes
Debt instrument stated interest rate	2.125%	2.125%
Issue Date	Mar. 06, 2018
Principal Amount \| €		€ 500,000,000
Price of Par Value	99.324%	99.324%
Discount	$ 4,200,000
Effective Interest Rate	2.208%	2.208%
Coupon Rate	2.125%
Maturity Date	Apr. 15, 2027
Unsecured senior notes, net	$ 616,100,000		$ 0

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

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
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Contractual interest rate for funds borrowed, under the debt agreement.

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Date the debt instrument was issued, in CCYY-MM-DD format.

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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt discount (premium).

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The rate of return due to the bond holder disclosed on the face of the debt instruments.

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The effective rate on par for debt issued during the period.

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