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Debt - Summary of Debt (Details) - USD ($) $ in Millions	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	$ 2,496.3	$ 2,645.7
Less current portion	0.0	150.0
Less unamortized debt issuance costs	12.6	15.3
Long-term debt	$ 2,483.7	$ 2,480.4
Weighted-average interest rate	3.64%	3.80%
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%
6.50% Senior Notes due March 2018 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt		$ 150.0
Stated interest rate	6.50%	6.50%
2.45% Senior Notes, due December 2020
Debt Instrument [Line Items]
Stated interest rate		2.45%
2.45% Senior Notes, due December 2020 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 499.6	$ 499.5
Stated interest rate	2.45%	2.45%	2.45%
3.90% Senior Notes, due June 2022 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 399.9	$ 399.8
Stated interest rate	3.90%	3.90%				3.90%
4.50% Senior Notes, due November 2023 \| Senior Notes
Debt Instrument [Line Items]
Long-term debt	$ 699.0	$ 698.8
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	$ 399.3	$ 399.2
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	$ 498.5	$ 498.4
Stated interest rate	3.40%	3.40%	3.40%
Current Portion of Long-term Debt
Debt Instrument [Line Items]
Weighted-average interest rate	0.00%	6.50%
Long-term Debt, Excluding Current Portion
Debt Instrument [Line Items]
Weighted-average interest rate	3.64%	3.64%