Income Taxes, Unrecognized tax benefits (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Taxes
Unrecognized tax benefits, anticipated adjustment for changing facts and circumstances, over the next twelve month period	$ 42.3
Amount for unrecognized tax benefits, including penalties and interest, which if recognized would impact the effective tax rate	171.0	$ 141.8
Reconciliation of the gross amounts of unrecognized tax benefits
Unrecognized tax benefits as of January 1	130.5	127.3	$ 106.2
Gross increases for tax positions in prior periods	20.9	18.9	32.7
Gross increases for tax positions in current period	9.0	2.0	2.4
Settlements	0.0	(14.1)	(11.0)
Lapse of statute of limitations	(1.3)	(3.6)	(3.0)
Unrecognized tax benefits at the end of the period	159.1	130.5	127.3
Estimated interest and penalties included in provision for income taxes	4.4	1.1	3.7
Tax-related interest and penalties liability for unrecognized tax benefits	$ 42.2	$ 40.5	$ 39.3