Income Taxes, Unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Taxes
Gross increases in unrecognized tax benefits related to acquisitions			$ 78.7
Reconciliation of the gross amounts of unrecognized tax benefits
Unrecognized tax benefits as of January 1	$ 127.3	$ 106.2	29.8
Gross increases for tax positions in prior periods	18.9	32.7	81.9
Gross increases for tax positions in current period	2.0	2.4	7.0
Settlements	(14.1)	(11.0)	(10.8)
Lapse of statute of limitations	(3.6)	(3.0)	(1.7)
Unrecognized tax benefits at the end of the period	130.5	127.3	106.2
Estimated interest and penalties included in provision for income taxes	1.1	3.7	6.5
Tax-related interest and penalties liability for unrecognized tax benefits	40.5	39.3	$ 35.3
Liability for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	141.8	$ 130.1
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 33.8