Indebtedness - Debt Repayment and Related Extinguishment (Details)									3 Months Ended		12 Months Ended
	Dec. 31, 2017 USD ($)	Dec. 12, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jul. 01, 2017 USD ($)	Jun. 15, 2017 USD ($)	May 23, 2017 USD ($)	May 08, 2017 USD ($)	Apr. 01, 2017 USD ($)	Dec. 31, 2017 EUR (€)	Jul. 01, 2017 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 USD ($)	Mar. 07, 2016 USD ($)	Dec. 05, 2014 EUR (€)	Dec. 05, 2014 USD ($)	Dec. 02, 2014 USD ($)	Nov. 08, 2013 USD ($)
Debt Instrument [Line Items]
Repayments of debt											$ 2,611,000,000
2014 Euro-Denominated Term Loan due December 5, 2019
Debt Instrument [Line Items]
Debt instrument, date of repayment	Dec. 31, 2017		Sep. 30, 2017	Jul. 01, 2017				Apr. 01, 2017	Dec. 31, 2017
Debt instrument, face amount														€ 500,000,000	$ 614,300,000
Debt instrument, description											2014 term loan due December 5, 2019
Debt instrument, transaction type				Scheduled quarterly payment				Scheduled quarterly payment
Repayments of debt	$ 15,000,000		$ 14,800,000	$ 14,300,000				$ 13,300,000
2.30% Unsecured Senior notes November 8, 2018
Debt Instrument [Line Items]
Debt instrument, date of repayment							May 08, 2017
Debt instrument, face amount																	$ 600,000,000.000
Interest rate, stated percentage									2.30%			2.30%					2.30%
Debt instrument, description							$600.0 2.300% senior notes due 2018
Debt instrument, transaction type							Early redemption
Repayments of debt							$ 600,000,000
4.5% Retail Bond
Debt Instrument [Line Items]
Debt instrument, date of repayment						May 23, 2017
Debt instrument, description						€180.0 4.500% retail bonds due 2017
Debt instrument, transaction type						Scheduled maturity
Repayments of debt						$ 201,300,000
3.5% Senior note due 2021
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Debt instrument, face amount																$ 500,000,000
Interest rate, stated percentage									3.50%			3.50%				3.50%
Debt instrument, description					$500.0 3.500% senior notes due 2021
Debt instrument, transaction type					Tender offer
Repayments of debt					$ 190,400,000
3.500% Unsecured Senior notes due March 15, 2021
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Debt instrument, face amount													$ 500,000,000.0
Interest rate, stated percentage									3.50%			3.50%	3.50%
Debt instrument, description					$500.0 3.500% senior notes due 2021
Debt instrument, transaction type					Tender offer
Repayments of debt					$ 219,600,000
4.00% Unsecured Senior Notes due November 15, 2023
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Debt instrument, face amount																	$ 800,000,000.000
Interest rate, stated percentage									4.00%			4.00%					4.00%
Debt instrument, description					$800.0 4.000% senior notes due 2023
Debt instrument, transaction type					Tender offer
Repayments of debt					$ 584,400,000					$ 584,400,000
5.30% Unsecured Senior Notes due November 15, 2043
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Debt instrument, face amount																	$ 400,000,000.000
Interest rate, stated percentage									5.30%			5.30%					5.30%
Debt instrument, description					$400.0 5.300% senior notes due 2043
Debt instrument, transaction type					Tender offer
Repayments of debt					$ 309,500,000					$ 309,500,000
4.9% Senior Loan due 2044
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Debt instrument, face amount																$ 400,000,000
Interest rate, stated percentage									4.90%			4.90%				4.90%
Debt instrument, description					$400.0 4.900% senior notes due 2044
Debt instrument, transaction type					Tender offer
Repayments of debt					$ 96,100,000
5.125% Senior note due 2017
Debt Instrument [Line Items]
Debt instrument, date of repayment		Dec. 12, 2017
Debt instrument, description		€300.0 5.125% senior notes due 2017
Debt instrument, transaction type		Scheduled maturity
Repayments of debt		$ 352,300,000
Senior Notes [Member] | Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 600,000,000
Interest rate, stated percentage									2.30%			2.30%
Senior Notes [Member] | Senior Note 1 due 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 500,000,000
Interest rate, stated percentage									3.50%			3.50%
Senior Notes [Member] | Senior Note 2 due 2021 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 500,000,000
Interest rate, stated percentage									3.50%			3.50%
Senior Notes [Member] | Senior Notes due 2023 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 800,000,000
Interest rate, stated percentage									4.00%			4.00%
Senior Notes [Member] | Senior Notes due 2043 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 400,000,000
Interest rate, stated percentage									5.30%			5.30%
Senior Notes [Member] | Senior Notes due 2044 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount												$ 400,000,000
Interest rate, stated percentage									4.90%			4.90%
Senior Notes [Member] | Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount | €									€ 300,000,000
Interest rate, stated percentage									5.125%			5.125%
Bonds [Member] | Retail Bonds due 2017 [Member]
Debt Instrument [Line Items]
Debt instrument, face amount | €									€ 180,000,000
Interest rate, stated percentage									4.50%			4.50%