Recently Issued and Adopted Accounting Pronouncements and Regulatory Items Revenue Recognition (Details) - USD ($) $ in Millions	Mar. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Assets
Prepaid and other current assets	$ 534.5		$ 326.4
Liabilities and Equity
Accrued and other liabilities	611.5		497.7
Accounting Standards Update 2014-09
Assets
Prepaid and other current assets	534.5	$ 411.2
Liabilities and Equity
Accrued and other liabilities	611.5	582.5
Accounting Standards Update 2014-09 | Adjustment due to ASC 606
Assets
Prepaid and other current assets	(95.9)
Liabilities and Equity
Accrued and other liabilities	(95.9)
Accounting Standards Update 2014-09 | Amounts without ASC 606 adjustment
Assets
Prepaid and other current assets	438.6
Liabilities and Equity
Accrued and other liabilities	$ 515.6
Amounts as originally reported | Accounting Standards Update 2014-09
Assets
Prepaid and other current assets			326.4
Liabilities and Equity
Accrued and other liabilities			$ 497.7
Adjustment | Accounting Standards Update 2014-09
Assets
Prepaid and other current assets		84.8
Liabilities and Equity
Accrued and other liabilities		$ 84.8