Shareholders' Equity (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Shareholders' Equity [Abstract]
Common stock repurchased during the period (in shares)	178,800	47,456	334,649	311,226
Common stock repurchased during the period, value	$ 14.4	$ 3.1	$ 26.7	$ 18.5