Present and Prospective Accounting Pronouncements Effect of change related to ASU 2016-18 (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities	$ (62.9)	$ (34.8)	$ (172.7)	$ (109.1)
Effect of exchange rate on cash, cash equivalents and restricted cash	(0.6)	1.8	(4.5)	1.7
Net increase in cash, cash equivalents and restricted cash	(14.2)	108.7	58.7	189.4
Cash, cash equivalents and restricted cash at beginning of period	1,014.2	753.2	941.3	672.5
Cash, cash equivalents and restricted cash at end of period	$ 1,000.0	861.9	$ 1,000.0	861.9
Scenario, Previously Reported [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities		(34.8)		(109.3)
Effect of exchange rate on cash, cash equivalents and restricted cash		1.8		1.9
Net increase in cash, cash equivalents and restricted cash		108.7		189.4
Cash, cash equivalents and restricted cash at beginning of period		740.0		659.3
Cash, cash equivalents and restricted cash at end of period		848.7		848.7
Accounting Standards Update 2017-07 [Member] | Scenario, Adjustment [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net cash used in investing activities		0.0		0.2
Effect of exchange rate on cash, cash equivalents and restricted cash		0.0		(0.2)
Net increase in cash, cash equivalents and restricted cash		0.0		0.0
Cash, cash equivalents and restricted cash at beginning of period		13.2		13.2
Cash, cash equivalents and restricted cash at end of period		$ 13.2		$ 13.2