Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Shareholders' Equity [Abstract]
Common stock repurchased during the period (in shares)	505,085	89,251	839,734	400,477
Common stock repurchased during the period, value	$ 37.7	$ 6.7	$ 64.5	$ 25.2