Contingencies - Schedule of Notes Receivable Balances from Insurance Companies (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Movement in Loss Contingency Receivable, Increase (Decrease) [Roll Forward]
Balance beginning of period	$ 67.3	$ 8.7
Additions	34.6	95.6
Collections	(23.5)	(37.0)
Balance end of period	$ 78.4	$ 67.3