Shareholders' Equity - Dividends (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended			9 Months Ended
	Oct. 31, 2016	Sep. 30, 2016	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Shareholders’ Equity
Dividends declared per common share (in dollars per share)	$ 0.16	$ 0.14	$ 0.14	$ 0.125	$ 0.42	$ 0.39
Dividends paid		$ 43.1	$ 38.6		$ 129.4	$ 116.1
Dividends declared		$ 43.2	$ 43.2		$ 129.5	$ 120.5