Debt, Commercial Paper (Details) € in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2019 EUR (€) item	Mar. 31, 2019 USD ($) item	Jan. 15, 2019 USD ($)	Dec. 31, 2018 USD ($)
Commercial Paper Programs
Debt
Maximum borrowing capacity			$ 2,500.0
U.S. Commercial Paper Program
Debt
Maturity term	397 days
Average interest rate (as a percent)	2.64%	2.64%
Debt carrying amount, net of unamortized discount before deferred debt issuance costs		$ 815.7		$ 554.5
Maximum borrowing capacity			$ 2,500.0
Euro Commercial Paper Program
Debt
Maturity term	183 days
Average interest rate (as a percent)	(0.10%)	(0.10%)
Number of wholly-owned subsidiaries that entered into a euro-commercial paper program | item	1	1
Debt carrying amount, net of unamortized discount before deferred debt issuance costs	€ 65.0	$ 72.9		$ 68.8
Maximum borrowing capacity		$ 2,000.0