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Debt - Summary of Debt (Details) - USD ($) $ in Millions	Dec. 31, 2019	Dec. 23, 2019	Dec. 06, 2019	Nov. 21, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 13, 2017	Sep. 05, 2014	Oct. 22, 2013	Jun. 26, 2012
Debt Instrument [Line Items]
Long-term debt	$ 2,493.1				$ 2,496.3
Less current portion	0.0				0.0
Less unamortized debt issuance costs	16.3				12.6
Long-term debt	$ 2,476.8				$ 2,483.7
Weighted-average interest rate	3.77%				3.64%
Revolving Credit Facility, due August 2021 \| Line of Credit
Debt Instrument [Line Items]
Long-term debt	$ 0.0				$ 0.0
Stated interest rate	0.00%				0.00%
2.45% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate	2.45%					2.45%
2.45% Senior Notes, due December 2020 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt					$ 499.6
Stated interest rate			2.45%	2.45%	2.45%		2.45%
3.90% Senior Notes, due June 2022
Debt Instrument [Line Items]
Stated interest rate	3.90%
3.90% Senior Notes, due June 2022 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt					$ 399.9
Stated interest rate		3.90%		3.90%	3.90%					3.90%
4.50% Senior Notes, due November 2023 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 699.2				$ 699.0
Stated interest rate	4.50%				4.50%				4.50%
3.65% Senior Notes, due September 2024 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 399.4				$ 399.3
Stated interest rate	3.65%				3.65%			3.65%
3.40% Senior Notes, due December 2027
Debt Instrument [Line Items]
Stated interest rate						3.40%
3.40% Senior Notes, due December 2027 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 498.7				$ 498.5
Stated interest rate	3.40%				3.40%		3.40%
3.00% Senior Notes, due December 2029
Debt Instrument [Line Items]
Stated interest rate	3.00%
3.00% Senior Notes, due December 2029 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 499.3
Stated interest rate	3.00%			3.00%
4.05% Senior Notes, due December 2049
Debt Instrument [Line Items]
Stated interest rate	4.05%
4.05% Senior Notes, due December 2049 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 396.5
Stated interest rate	4.05%			4.05%
Current Portion of Long-term Debt
Debt Instrument [Line Items]
Weighted-average interest rate	0.00%				0.00%
Long-term Debt, Excluding Current Portion
Debt Instrument [Line Items]
Weighted-average interest rate	3.77%				3.64%