Restructuring - Restructuring Reserve Activity (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring accrual balances and related activity
Balance at beginning of period	$ 89.9	$ 4.7	$ 7.6
Liabilities incurred	49.4	59.4	21.2
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Restructuring Liabilities	(8.2)	45.5
Liabilities paid/settled	(77.1)	(19.7)	(24.1)
Balance at end of period	$ 54.0	$ 89.9	$ 4.7