Summary of Total Indebtedness (Detail) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Principal Amount	$ 5,554.9	$ 5,580.4
Fair Value of Interest Rate Swap	(12.2)	(3.0)
Unamortized (Discount) Premium	(8.9)	(9.4)
Unamortized Debt Issuance Costs	(26.2)	(27.5)
Total Debt	5,507.6	5,540.5
Current portion	(389.6)	(429.4)
Carrying Amount	5,417.7	5,410.6
Current portion of long-term debt	(299.7)	(299.5)
Total long-term debt, non-current	5,118.0	5,111.1
Commercial Paper [Member]
Debt Instrument [Line Items]
Principal Amount	90.0	130.0
Unamortized (Discount) Premium	(0.1)	(0.1)
Total Debt	89.9	129.9
2010 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Fair Value of Interest Rate Swap	(5.6)
Unamortized (Discount) Premium	(0.9)	(1.0)
Unamortized Debt Issuance Costs	(1.0)	(1.2)
Carrying Amount	492.5	497.8
2012 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Fair Value of Interest Rate Swap	(2.3)	(0.8)
Unamortized (Discount) Premium	(1.9)	(2.0)
Unamortized Debt Issuance Costs	(1.7)	(1.7)
Carrying Amount	494.1	495.5
2013 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Unamortized (Discount) Premium	(1.8)	(1.8)
Unamortized Debt Issuance Costs	(2.3)	(2.4)
Carrying Amount	495.9	495.8
2014 Senior Notes (5-Year) [Member]
Debt Instrument [Line Items]
Principal Amount	450.0	450.0
Fair Value of Interest Rate Swap	(4.3)	(2.2)
Unamortized (Discount) Premium	(0.2)	(0.2)
Unamortized Debt Issuance Costs	(0.9)	(1.1)
Carrying Amount	444.6	446.5
2014 Senior Notes (30-Year) [Member]
Debt Instrument [Line Items]
Principal Amount	600.0	600.0
Unamortized (Discount) Premium	3.3	3.3
Unamortized Debt Issuance Costs	(5.6)	(5.7)
Carrying Amount	597.7	597.6
2015 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	614.9	600.4
Unamortized Debt Issuance Costs	(3.5)	(3.6)
Carrying Amount	611.4	596.8
2017 Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Unamortized (Discount) Premium	(1.2)	(1.3)
Unamortized Debt Issuance Costs	(3.0)	(3.2)
Carrying Amount	495.8	495.5
2017 Floating Rate Senior Notes [Member]
Debt Instrument [Line Items]
Principal Amount	300.0	300.0
Unamortized Debt Issuance Costs	(0.3)	(0.5)
Carrying Amount	299.7	299.5
2.625% 2017 Notes, due 2023 [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Unamortized (Discount) Premium	(1.0)	(1.1)
Unamortized Debt Issuance Costs	(3.4)	(3.5)
Carrying Amount	495.6	495.4
3.25% 2017 Notes, due 2028 [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Unamortized (Discount) Premium	(5.1)	(5.2)
Unamortized Debt Issuance Costs	(3.9)	(3.9)
Carrying Amount	491.0	490.9
2017 Term Loan Facility, due 2020 [Member]
Debt Instrument [Line Items]
Principal Amount	500.0	500.0
Unamortized Debt Issuance Costs	(0.6)	(0.7)
Carrying Amount	$ 499.4	$ 499.3

Amount of short-term debt and current maturity of long-term debt and capital lease obligations due within one year or the normal operating cycle, if longer.

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