Income Taxes (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Provisional amount, tax benefit	$ 2.0		$ (2.0)
Income tax expense	$ 54.7	$ 77.6	$ 150.2	$ 148.4
Effective income tax rate reconciliation, percent	22.90%	37.50%	23.70%	31.10%