Indebtedness - Borrowings Outstanding (Details) - USD ($)									3 Months Ended	12 Months Ended
		Dec. 31, 2017	Sep. 30, 2017	Jul. 01, 2017	Jun. 15, 2017	May 08, 2017	Apr. 01, 2017	Dec. 02, 2014	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Sep. 26, 2016	Mar. 07, 2016	Dec. 31, 2015	Jun. 27, 2015	Nov. 08, 2013	Sep. 06, 2013
Debt Instrument [Line Items]
Revolving credit agreements		$ 0							$ 0	$ 0	$ 0				$ 680,000,000
Term loans															300,000,000		$ 1,000,000,000
Senior notes		2,906,000,000							2,906,000,000	2,906,000,000	5,373,100,000				4,698,300,000	$ 2,300,000,000
Other financing		11,700,000							11,700,000	11,700,000	3,600,000				128,200,000
Unamortized premium (discount), net		21,400,000							21,400,000	21,400,000	33,000,000				73,400,000
Deferred financing fees		(17,900,000)							(17,900,000)	(17,900,000)	(33,100,000)				(36,600,000)
Total borrowings outstanding		3,341,200,000							3,341,200,000	3,341,200,000	5,797,300,000				6,032,100,000
Current indebtedness		(70,400,000)							(70,400,000)	(70,400,000)	(572,800,000)				(1,060,500,000)
Total long-term debt, less current portion		3,270,800,000							3,270,800,000	3,270,800,000	5,224,500,000			$ 4,971,600,000	4,971,600,000
2015 Revolver
Debt Instrument [Line Items]
Revolving credit agreements		0							0	0	0				380,000,000
2014 Revolver
Debt Instrument [Line Items]
Revolving credit agreements		$ 0							$ 0	0	0				300,000,000
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
Term loans	[1]	$ 420,000,000							$ 420,000,000	$ 420,000,000	420,700,000				488,800,000
1.30% Unsecured Senior Notes due November 8, 2016
Debt Instrument [Line Items]
Interest rate, stated percentage		1.30%							1.30%	1.30%		1.30%				1.30%
Maturity date										Nov. 08, 2016
Senior notes	[2]	$ 0							$ 0	$ 0	0				500,000,000
4.500% Unsecured Senior Notes due May 23, 2017
Debt Instrument [Line Items]
Interest rate, stated percentage		4.50%							4.50%	4.50%
Maturity date										May 23, 2017
Senior notes	[1],[3]	$ 0							$ 0	$ 0	189,300,000				195,500,000
5.125% Unsecured Senior Notes due December 12, 2017
Debt Instrument [Line Items]
Interest rate, stated percentage		5.125%							5.125%	5.125%
Maturity date										Dec. 12, 2017
Senior notes	[1],[3]	$ 0							$ 0	$ 0	315,600,000				325,800,000
2.30% Unsecured Senior notes November 8, 2018
Debt Instrument [Line Items]
Debt instrument, date of repayment						May 08, 2017
Interest rate, stated percentage		2.30%							2.30%	2.30%						2.30%
Maturity date										Nov. 08, 2018
Senior notes	[2]	$ 0							$ 0	$ 0	600,000,000				600,000,000
5.000% Unsecured Senior notes due May 23, 2019
Debt Instrument [Line Items]
Interest rate, stated percentage		5.00%							5.00%	5.00%
Maturity date										May 23, 2019
Senior notes	[1],[3]	$ 144,000,000							$ 144,000,000	$ 144,000,000	126,200,000				130,300,000
3.500% Unsecured Senior notes due March 15, 2021
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Interest rate, stated percentage		3.50%							3.50%	3.50%			3.50%
Maturity date										Mar. 15, 2021
Senior notes	[4]	$ 280,400,000							$ 280,400,000	$ 280,400,000	500,000,000				0
3.5% Senior note due 2021
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Interest rate, stated percentage		3.50%						3.50%	3.50%	3.50%
Maturity date								Jan. 01, 2021		Dec. 15, 2021
Senior notes	[5]	$ 309,600,000							$ 309,600,000	$ 309,600,000	500,000,000				500,000,000
5.105% Senior note due July 19, 2023
Debt Instrument [Line Items]
Interest rate, stated percentage		5.1045%							5.1045%	5.1045%
Maturity date										Jul. 19, 2023
Senior notes	[1],[3]	$ 162,000,000							$ 162,000,000	$ 162,000,000	142,000,000				146,700,000
4.00% Unsecured Senior Notes due November 15, 2023
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Interest rate, stated percentage		4.00%							4.00%	4.00%						4.00%
Maturity date										Nov. 15, 2023
Senior notes	[2]	$ 215,600,000							$ 215,600,000	$ 215,600,000	800,000,000				800,000,000
3.9% senior note due 2024
Debt Instrument [Line Items]
Interest rate, stated percentage		3.90%						3.90%	3.90%	3.90%
Maturity date								Jan. 01, 2024		Dec. 15, 2024
Senior notes	[5]	$ 700,000,000							$ 700,000,000	$ 700,000,000	700,000,000				700,000,000
4.375% senior note due March 15, 2026
Debt Instrument [Line Items]
Interest rate, stated percentage		4.375%							4.375%	4.375%			4.375%
Maturity date										Mar. 15, 2026
Senior notes	[4]	$ 700,000,000							$ 700,000,000	$ 700,000,000	700,000,000				0
5.30% Unsecured Senior Notes due November 15, 2043
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Interest rate, stated percentage		5.30%							5.30%	5.30%						5.30%
Maturity date										Nov. 15, 2043
Senior notes	[2]	$ 90,500,000							$ 90,500,000	$ 90,500,000	400,000,000				400,000,000
4.9% Senior Loan due 2044
Debt Instrument [Line Items]
Debt instrument, date of repayment					Jun. 15, 2017
Interest rate, stated percentage		4.90%						4.90%	4.90%	4.90%
Maturity date								Jan. 01, 2044		Dec. 15, 2044
Senior notes	[5]	$ 303,900,000							$ 303,900,000	$ 303,900,000	$ 400,000,000				$ 400,000,000

[1] Debt denominated in euros subject to fluctuations in the euro-to-U.S. dollar exchange rate.

[2] Discussed below collectively as the "2013 Notes."

[3] Debt assumed from Omega.

[4] Discussed below collectively as the "2016 Notes."

[5] Discussed below collectively as the "2014 Notes."