Commitments (Details) $ in Millions	Sep. 30, 2018 USD ($)
Other Commitments [Line Items]
Letters of Credit Outstanding, Amount	$ 74.3
Revolving Credit Facility [Member]
Other Commitments [Line Items]
Letters of Credit Outstanding, Amount	47.9
Cash and Cash Equivalents [Member]
Other Commitments [Line Items]
Pledged Assets, Not Separately Reported, Other	3.7
Guarantee Type, Other [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	23.2
Performance Guarantee [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	29.4
Indemnification Agreement [Member]
Other Commitments [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 318.0