Shareholders' Equity, Dividends (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended	3 Months Ended			6 Months Ended
	Sep. 30, 2016	Jul. 31, 2017	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Shareholders’ Equity
Dividends declared per common share (in dollars per share)	$ 0.14	$ 0.19	$ 0.16	$ 0.16	$ 0.14	$ 0.32	$ 0.28
Dividends paid			$ 48.9		$ 43.0	$ 98.2	$ 86.3
Dividends declared			$ 48.8		$ 43.2	$ 97.8	$ 86.3