Credit Facilities (Details) $ in Millions	3 Months Ended
	Mar. 31, 2021 USD ($) Rate
Committed credit facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 1,500.0
Line of Credit Facility, Available Capacity Increase Amount	250.0
Line of Credit Facility, Limit on Letters of Credit	50.0
Line of Credit Outstanding, Amount	0.0
Letters of Credit Outstanding, Amount	10.0
Line of Credit Facility, Remaining Borrowing Capacity	1,490.0
Uncommitted credit facility [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	927.9
Line of Credit Outstanding, Amount	43.1
Line of Credit Facility, Average Outstanding Amount	$ 81.4
Short-term Debt, Weighted Average Interest Rate, over Time	2.90%
364 Day [Member]
Short-term Debt [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 500.0
Margin for base rate advances | Rate	0.25%
Margin for Eurocurrency rate advances | Rate	1.25%
Line of Credit Facility, Commitment Fee Percentage | Rate	0.25%